Correlation of gestational age and age at death in sudden infant death syndrome: another pointer to the role of critical developmental period?

BACKGROUND: Filiano and Kinney proposed a triple-risk model for the sudden infant death syndrome (SIDS) that involves the intersection of three risks: (1) a vulnerable infant, (2) a critical developmental period in homeostatic control, and (3) an exogenous stressor(s). The primary evidence for the role of a critical developmental period in SIDS etiology is the peak of cases around the third month of life. Independently, several studies pointed to correlation between gestational age and age at death in SIDS, but used that to assess the SIDS risk for preterm infants, ignoring further ramifications. METHODS: We did a detailed analysis of CDC data spanning over two decades (1983-2011). We focused not only on the correlation between two age variables (gestational and age at death), but also on the possibility of misdiagnosis. Also, we attempted to account for potential biases in the data induced by the ICD-9/ICD-190 transition or the "Back to Sleep" campaign. RESULTS: The peak of deaths in the third month of life, that was the main argument for the role of the critical development period, wasn't unique to SIDS. However, we confirmed an almost linear and negative correlation between gestational age and the week of death due to SIDS. This pattern (slope of correlation < 0 and significance of correlation p < 0.05) is characteristic of SIDS among all diseases analyzed in the study. CONCLUSIONS: We interpret the results as the evidence of the role of the critical development period in SIDS etiology. Possibly more attention in the future research should be put to theories that are based on homeostatic control.

Two novel C-terminal frameshift mutations in the ß-globin gene lead to rapid mRNA decay.

BACKGROUND: The thalassemia syndromes are classified according to the globin chain or chains whose production is affected. ß-thalassemias are caused by point mutations or, more rarely, deletions or insertions of a few nucleotides in the ß-globin gene or its immediate flanking sequences. These mutations interfere with the gene function either at the transcriptional, translational or posttranslational level. METHODS: Two cases of Polish patients with hereditary hemolytic anemia suspected of thalassemia were studied. DNA sequencing and mRNA quantification were performed. Stable human cell lines which express wild-type HBB and mutated versions were used to verify that detected mutation are responsible for mRNA degradation. RESULTS: We identified two different frameshift mutations positioned in the third exon of HBB. Both patients harboring these mutations present the clinical phenotype of thalassemia intermedia and showed dominant pattern of inheritance. In both cases the mutations do not generate premature stop codon. Instead, slightly longer protein with unnatural C-terminus could be produced. Interestingly, although detected mutations are not expected to induce NMD, the mutant version of mRNA is not detectable. Restoring of the open reading frame brought back the RNA to that of the wild-type level. CONCLUSION: Our results show that a lack of natural stop codon due to the frameshift in exon 3 of ß-globin gene causes rapid degradation of its mRNA and indicate existence of novel surveillance pathway.

Genome sequence and analysis of the tuber crop potato.

Potato (Solanum tuberosum L.) is the world's most important non-grain food crop and is central to global food security. It is clonally propagated, highly heterozygous, autotetraploid, and suffers acute inbreeding depression. Here we use a homozygous doubled-monoploid potato clone to sequence and assemble 86% of the 844-megabase genome. We predict 39,031 protein-coding genes and present evidence for at least two genome duplication events indicative of a palaeopolyploid origin. As the first genome sequence of an asterid, the potato genome reveals 2,642 genes specific to this large angiosperm clade. We also sequenced a heterozygous diploid clone and show that gene presence/absence variants and other potentially deleterious mutations occur frequently and are a likely cause of inbreeding depression. Gene family expansion, tissue-specific expression and recruitment of genes to new pathways contributed to the evolution of tuber development. The potato genome sequence provides a platform for genetic improvement of this vital crop.

Engineering high Zn in tomato shoots through expression of AtHMA4 involves tissue-specific modification of endogenous genes.

BACKGROUND: To increase the Zn level in shoots, AtHMA4 was ectopically expressed in tomato under the constitutive CaMV 35S promoter. However, the Zn concentration in the shoots of transgenic plants failed to increase at all tested Zn levels in the medium. Modification of Zn root/shoot distribution in tomato expressing 35S::AtHMA4 depended on the concentration of Zn in the medium, thus indicating involvement of unknown endogenous metal-homeostasis mechanisms. To determine these mechanisms, those metal-homeostasis genes that were expressed differently in transgenic and wild-type plants were identified by microarray and RT-qPCR analysis using laser-assisted microdissected RNA isolated from two root sectors: (epidermis + cortex and stele), and leaf sectors (upper epidermis + palisade parenchyma and lower epidermis + spongy parenchyma). RESULTS: Zn-supply-dependent modification of Zn root/shoot distribution in AtHMA4-tomato (increase at 5 µM Zn, no change at 0.5 µM Zn) involved tissue-specific, distinct from that in the wild type, expression of tomato endogenous genes. First, it is suggested that an ethylene-dependent pathway underlies the detected changes in Zn root/shoot partitioning, as it was induced in transgenic plants in a distinct way depending on Zn exposure. Upon exposure to 5 or 0.5 µM Zn, in the epidermis + cortex of the transgenics' roots the expression of the Strategy I Fe-uptake system (ethylene-dependent LeIRT1 and LeFER) was respectively lower or higher than in the wild type and was accompanied by respectively lower or higher expression of the identified ethylene genes (LeNR, LeACO4, LeACO5) and of LeChln. Second, the contribution of LeNRAMP2 expression in the stele is shown to be distinct for wild-type and transgenic plants at both Zn exposures. Ethylene was also suggested as an important factor in a pathway induced in the leaves of transgenic plants by high Zn in the apoplast, which results in the initiation of loading of the excess Zn into the mesophyll of "Zn accumulating cells". CONCLUSIONS: In transgenic tomato plants, the export activity of ectopically expressed AtHMA4 changes the cellular Zn status, which induces coordinated tissue-specific responses of endogenous ethylene-related genes and metal transporters. These changes constitute an important mechanism involved in the generation of the metal-related phenotype of transgenic tomato expressing AtHMA4.

Adhesion of the genome-sequenced Lactococcus lactis subsp. cremoris IBB477 strain is mediated by specific molecular determinants.

Understanding the nature of mucus-microbe interactions will provide important information that can help to elucidate the mechanisms underlying probiotic adhesion. This study focused on the adhesive properties of the Lactococcus lactis subsp. cremoris IBB477 strain, previously shown to persist in the gastrointestinal tract of germ-free rats. The shear flow-induced detachment of L. lactis cells was investigated under laminar flow conditions. Such a dynamic approach demonstrated increased adhesion to bare and mucin-coated polystyrene for IBB477, compared to that observed for the MG1820 control strain. To identify potential genetic determinants giving adhesive properties to IBB477, the improved high-quality draft genome sequence comprising chromosome and five plasmids was obtained and analysed. The number of putative adhesion proteins was determined on the basis of surface/extracellular localisation and/or the presence of adhesion domains. To identify proteins essential for the IBB477 specific adhesion property, nine deletion mutants in chromosomal genes have been constructed and analysed using adhesion tests on bare polystyrene as well as mucin-, fibronectin- or collagen IV-coated polystyrene plates in comparison to the wild-type strain. These experiments demonstrated that gene AJ89_07570 encoding a protein containing DUF285, MucBP and four Big_3 domains is involved in adhesion to bare and mucin-coated polystyrene. To summarise, in the present work, we characterised the adhesion of IBB477 under laminar flow conditions; identified the putative adherence factors present in IBB477, which is the first L. lactis strain exhibiting adhesive and mucoadhesive properties to be sequenced and demonstrated that one of the proteins containing adhesion domains contributes to adhesion.

The evolutionary rate of antibacterial drug targets.

BACKGROUND: One of the major issues in the fight against infectious diseases is the notable increase in multiple drug resistance in pathogenic species. For that reason, newly acquired high-throughput data on virulent microbial agents attract the attention of many researchers seeking potential new drug targets. Many approaches have been used to evaluate proteins from infectious pathogens, including, but not limited to, similarity analysis, reverse docking, statistical 3D structure analysis, machine learning, topological properties of interaction networks or a combination of the aforementioned methods. From a biological perspective, most essential proteins (knockout lethal for bacteria) or highly conserved proteins (broad spectrum activity) are potential drug targets. Ribosomal proteins comprise such an example. Many of them are well-known drug targets in bacteria. It is intuitive that we should learn from nature how to design good drugs. Firstly, known antibiotics are mainly originating from natural products of microorganisms targeting other microorganisms. Secondly, paleontological data suggests that antibiotics have been used by microorganisms for million years. Thus, we have hypothesized that good drug targets are evolutionary constrained and are subject of evolutionary selection. This means that mutations in such proteins are deleterious and removed by selection, which makes them less susceptible to random development of resistance. Analysis of the speed of evolution seems to be good approach to test this hypothesis. RESULTS: In this study we show that pN/pS ratio of genes coding for known drug targets is significantly lower than the genome average and also lower than that for essential genes identified by experimental methods. Similar results are observed in the case of dN/dS analysis. Both analyzes suggest that drug targets tend to evolve slowly and that the rate of evolution is a better predictor of drugability than essentiality. CONCLUSIONS: Evolutionary rate can be used to score and find potential drug targets. The results presented here may become a useful addition to a repertoire of drug target prediction methods. As a proof of concept, we analyzed GO enrichment among the slowest evolving genes. These may become the starting point in the search for antibiotics with a novel mechanism.

Recurrent horizontal transfer of bacterial toxin genes to eukaryotes.

In this work, we report likely recurrent horizontal (lateral) gene transfer events of genes encoding pore-forming toxins of the aerolysin family between species belonging to different kingdoms of life. Clustering based on pairwise similarity and phylogenetic analysis revealed several distinct aerolysin sequence groups, each containing proteins from multiple kingdoms of life. These results strongly support at least six independent transfer events between distantly related phyla in the evolutionary history of one protein family and discount selective retention of ancestral genes as a plausible explanation for this patchy phylogenetic distribution. We discuss the possible roles of these proteins and show evidence for a convergent new function in two extant species. We hypothesize that certain gene families are more likely to be maintained following horizontal gene transfer from commensal or pathogenic organism to its host if they 1) can function alone; and 2) are immediately beneficial for the ecology of the organism, as in the case of pore-forming toxins which can be utilized in multicellular organisms for defense and predation.

Proteins contribute insignificantly to the intrinsic buffering capacity of yeast cytoplasm.

Intracellular pH is maintained by a combination of the passive buffering of cytoplasmic dissociable compounds and several active systems. Over the years, a large portion of and possibly most of the cell's intrinsic (i.e., passive non-bicarbonate) buffering effect was attributed to proteins, both in higher organisms and in yeast. This attribution was not surprising, given that the concentration of proteins with multiple protonable/deprotonable groups in the cell exceeds the concentration of free protons by a few orders of magnitude. Using data from both high-throughput experiments and in vitro laboratory experiments, we tested this concept. We assessed the buffering capacity of the yeast proteome using protein abundance data and compared it to our own titration of yeast cytoplasm. We showed that the protein contribution is less than 1% of the total intracellular buffering capacity. As confirmed with NMR measurements, inorganic phosphates play a crucial role in the process. These findings also shed a new light on the role of proteomes in maintaining intracellular pH. The contribution of proteins to the intrinsic buffering capacity is negligible, and proteins might act only as a recipient of signals for changes in pH.

The relationship between EMG high frequency and low frequency band amplitude changes correlates with tissue inorganic phosphate levels.

Assessing inorganic phosphate levels seems crucial in deciphering the biochemical state of organisms or tissues. The concentration of inorganic phosphate in blood is an order of magnitude smaller than in tissues and, on top of that, it is dynamically used to fill temporary gaps in tissues. This is the reason blood inorganic phosphate level is considered a poor proxy for tissue levels. Therefore, tissue biopsy seems to be the dominant method when assessing inorganic phosphate levels for instance in muscles. In this study, we attempted to derive a non-invasive biomarker for phosphate tissue levels. We analyzed surface electromyography signals taken during 31P spectroscopy of leg muscles in five adult pigs. We induced hypophosphatemia via 20 minutes-long hyperventilation. It turned out that the proportion of the amplitude of the low frequency band and the high frequency band is significantly (p=0.002) correlated with the relative phosphate levels. The electromyographic signal did not correlate significantly with pCO2 levels in the blood, suggesting that the changes in the signal are a result of inorganic phosphate levels, not hyperventilation. The results might lead to the development of a real-time phosphate fluctuations measurement procedure.

Independent subtilases expansions in fungi associated with animals.

Many socially important fungi encode an elevated number of subtilisin-like serine proteases, which have been shown to be involved in fungal mutualisms with grasses and in parasitism of insects, nematodes, plants, other fungi, and mammalian skin. These proteins have endopeptidase activities and constitute a significant part of fungal secretomes. Here, we use comparative genomics to investigate the relationship between the quality and quantity of serine proteases and the ability of fungi to cause disease in invertebrate and vertebrate animals. Our screen of previously unexamined fungi allowed us to annotate and identify nearly 1000 subtilisin-containing proteins and to describe six new categories of serine proteases. Architectures of predicted proteases reveal novel combinations of subtilisin domains with other, co-occurring domains. Phylogenetic analysis of the most common clade of fungal proteases, proteinase K, showed that gene family size changed independently in fungi, pathogenic to invertebrates (Hypocreales) and vertebrates (Onygenales). Interestingly, simultaneous expansions in the S8 and S53 families of subtilases in a single fungal species are rare. Our analysis finds that closely related systemic human pathogens may not show the same gene family expansions, and that related pathogens and nonpathogens may show the same type of gene family expansion. Therefore, the number of proteases does not appear to relate to pathogenicity. Instead, we hypothesize that the number of fungal serine proteases in a species is related to the use of the animal as a food source, whether it is dead or alive.

Biodiversity in Oscypek, a traditional Polish cheese, determined by culture-dependent and -independent approaches.

Oscypek is a traditional Polish scalded-smoked cheese, with a protected-designation-of-origin (PDO) status, manufactured from raw sheep's milk without starter cultures in the Tatra Mountains region of Poland. This study was undertaken in order to gain insight into the microbiota that develops and evolves during the manufacture and ripening stages of Oscypek. To this end, we made use of both culturing and the culture-independent methods of PCR followed by denaturing gradient gel electrophoresis (PCR-DGGE) and pyrosequencing of 16S rRNA gene amplicons. The culture-dependent technique and PCR-DGGE fingerprinting detected the predominant microorganisms in traditional Oscypek, whereas the next-generation sequencing technique (454 pyrosequencing) revealed greater bacterial diversity. Besides members of the most abundant bacterial genera in dairy products, e.g., Lactococcus, Lactobacillus, Leuconostoc, Streptococcus, and Enterococcus, identified by all three methods, other, subdominant bacteria belonging to the families Bifidobacteriaceae and Moraxellaceae (mostly Enhydrobacter), as well as various minor bacteria, were identified by pyrosequencing. The presence of bifidobacterial sequences in a cheese system is reported for the first time. In addition to bacteria, a great diversity of yeast species was demonstrated in Oscypek by the PCR-DGGE method. Culturing methods enabled the determination of a number of viable microorganisms from different microbial groups and their isolation for potential future applications in specific cheese starter cultures.

Structure of the head of the Bartonella adhesin BadA.

Trimeric autotransporter adhesins (TAAs) are a major class of proteins by which pathogenic proteobacteria adhere to their hosts. Prominent examples include Yersinia YadA, Haemophilus Hia and Hsf, Moraxella UspA1 and A2, and Neisseria NadA. TAAs also occur in symbiotic and environmental species and presumably represent a general solution to the problem of adhesion in proteobacteria. The general structure of TAAs follows a head-stalk-anchor architecture, where the heads are the primary mediators of attachment and autoagglutination. In the major adhesin of Bartonella henselae, BadA, the head consists of three domains, the N-terminal of which shows strong sequence similarity to the head of Yersinia YadA. The two other domains were not recognizably similar to any protein of known structure. We therefore determined their crystal structure to a resolution of 1.1 A. Both domains are beta-prisms, the N-terminal one formed by interleaved, five-stranded beta-meanders parallel to the trimer axis and the C-terminal one by five-stranded beta-meanders orthogonal to the axis. Despite the absence of statistically significant sequence similarity, the two domains are structurally similar to domains from Haemophilus Hia, albeit in permuted order. Thus, the BadA head appears to be a chimera of domains seen in two other TAAs, YadA and Hia, highlighting the combinatorial evolutionary strategy taken by pathogens.

From the index case to global spread: the global mobility based modelling of the COVID-19 pandemic implies higher infection rate and lower detection ratio than current estimates.

BACKGROUND: Since the outbreak of the COVID-19 pandemic, multiple efforts of modelling of the geo-temporal transmissibility of the virus have been undertaken, but none describes the pandemic spread at the global level. The aim of this research is to provide a high-resolution global model of the pandemic that overcomes the problem of biased country-level data on the number of infected cases. To achieve this we propose a novel SIR-type metapopulation transmission model and a set of analytically derived model parameters. We used them to perform a simulation of the disease spread with help of the Global Epidemic and Mobility (GLEAM) framework embedding actual population densities, commute patterns and long-range travel networks. The simulation starts on 17 November 2019 with the index case (presymptomatic, yet infectious) in Wuhan, China, and results in an accurate prediction of the number of diagnosed cases after 154 days in multiple countries across five continents. In addition, the model outcome shows high compliance with the results of a random screening test conducted on pregnant women in the New York area. METHODS: We have built a modified SIR metapopulation transmission model and parameterized it analytically either by setting the values of the parameters based on the literature, or by assuming their plausible values. We compared our results with the number of diagnosed cases in twenty selected countries, ones which provide reliable statistics but differ substantially in terms of strength and speed of undertaken Non-Drug Interventions. The obtained 95% confidence intervals for the predictions are in agreement with the empirical data. RESULTS: The parameters that successfully model the pandemic are: the basic reproduction number R 0, 4.4; a latent non-infectious period of 1.1. days followed by 4.6 days of the presymptomatic infectious period; the probability of developing severe symptoms, 0.01; the probability of being diagnosed when presenting severe symptoms of 0.6; the probability of diagnosis for cases with mild symptoms or asymptomatic, 0.001. DISCUSSION: Parameters that successfully reproduce the observed number of cases indicate that both R 0 and the prevalence of the virus might be underestimated. This is in concordance with the newest research on undocumented COVID-19 cases. Consequently, the actual mortality rate is putatively lower than estimated. Confirmation of the pandemic characteristic by further refinement of the model and screening tests is crucial for developing an effective strategy for the global epidemiological crisis.

Stress-Induced Phosphaturia in Weaned Piglets.

The weaning period in piglets draws significant attention from researchers, veterinarians, and breeders. A substantial change in diet accompanied by enormous stress has health and welfare implications (abnormal feeding intake, infections, umbilical lesions, etc.). While the parameters like optimal age or weight for the weaning have been studied extensively, relatively less attention has been devoted to the study of stress effects in the piglets' biochemistry. As one of the effects of stress is hyperventilation, a gasometric analysis supported by measurements of hypoxia biomarkers was conducted. Piglets blood and urine, one day and seven days before and one day and seven days after the weaning, were tested. There was no evidence of hyperventilation, but phosphaturia and hypophosphatemia were observed one and seven days postweaning, respectively. A statistical analysis across the population also pointed to minor tissue hypoxia. Our work contributes to an understanding of biochemical dynamics and helps in the interpretation of physiological changes observed in piglets in this critical period.

Plasmodium falciparum translational machinery condones polyadenosine repeats.

Plasmodium falciparum is a causative agent of human malaria. Sixty percent of mRNAs from its extremely AT-rich (81%) genome harbor long polyadenosine (polyA) runs within their ORFs, distinguishing the parasite from its hosts and other sequenced organisms. Recent studies indicate polyA runs cause ribosome stalling and frameshifting, triggering mRNA surveillance pathways and attenuating protein synthesis. Here, we show that P. falciparum is an exception to this rule. We demonstrate that both endogenous genes and reporter sequences containing long polyA runs are efficiently and accurately translated in P. falciparum cells. We show that polyA runs do not elicit any response from No Go Decay (NGD) or result in the production of frameshifted proteins. This is in stark contrast to what we observe in human cells or T. thermophila, an organism with similar AT-content. Finally, using stalling reporters we show that Plasmodium cells evolved not to have a fully functional NGD pathway.

Domain annotation of trimeric autotransporter adhesins--daTAA.

MOTIVATION: Trimeric autotransporter adhesins (TAAs), such as Yersinia YadA, Neisseria NadA, Moraxella UspAs, Haemophilus Hia and Bartonella BadA, are important pathogenicity factors of proteobacteria. Their high sequence diversity and distinct mosaic-like structure lead to difficulties in the annotation of their sequences. These stem from the large number of short repeats, the presence of compositionally unusual coiled-coils, fuzzy domain boundaries and regions of seemingly low sequence complexity. RESULTS: We have developed a workflow, named daTAA, for the accurate domain annotation of TAAs. Its core consists of manually curated alignments and of knowledge-based rules that enhance assignments made by sequence similarity. Compared to general domain annotation servers such as PFAM, daTAA captures more domains and provides more sensitive domain detection, as well as integrated and detailed coiled-coil assignments. AVAILABILITY: The daTAA server is freely accessible at http://toolkit.tuebingen.mpg.de/dataa

Combined in silico and 19F NMR analysis of 5-fluorouracil metabolism in yeast at low ATP conditions.

The cytotoxic effect of 5-fluorouracil (5-FU) on yeast cells is thought to be mainly via a misincorporation of fluoropyrimidines into both RNA and DNA, not only DNA damage via inhibition of thymidylate synthase (TYMS) by fluorodeoxyuridine monophosphate (FdUMP). However, some studies on Saccharomyces cerevisiae show a drastic decrease in ATP concentration under oxidative stress, together with a decrease in concentration of other tri- and diphosphates. This raises a question if hydrolysis of 5-fluoro-2-deoxyuridine diphosphate (FdUDP) under oxidative stress could not lead to the presence of FdUMP and the activation of so-called 'thymine-less death' route. We attempted to answer this question with in silico modeling of 5-FU metabolic pathways, based on new experimental results, where the stages of intracellular metabolism of 5-FU in Saccharomyces cerevisiae were tracked by a combination of 19F and 31P NMR spectroscopic study. We have identified 5-FU, its nucleosides and nucleotides, and subsequent di- and/or triphosphates. Additionally, another wide 19F signal, assigned to fluorinated unstructured short RNA, has been also identified in the spectra. The concentration of individual metabolites was found to vary substantially within hours, however, the initial steady-state was preserved only for an hour, until the ATP concentration dropped by a half, which was monitored independently via 31P NMR spectra. After that, the catabolic process leading from triphosphates through monophosphates and nucleosides back to 5-FU was observed. These results imply careful design and interpretation of studies in 5-FU metabolism in yeast.

A short translational ramp determines the efficiency of protein synthesis.

Translation initiation is a major rate-limiting step for protein synthesis. However, recent studies strongly suggest that the efficiency of protein synthesis is additionally regulated by multiple factors that impact the elongation phase. To assess the influence of early elongation on protein synthesis, we employed a library of more than 250,000 reporters combined with in vitro and in vivo protein expression assays. Here we report that the identity of the amino acids encoded by codons 3 to 5 impact protein yield. This effect is independent of tRNA abundance, translation initiation efficiency, or overall mRNA structure. Single-molecule measurements of translation kinetics revealed pausing of the ribosome and aborted protein synthesis on codons 4 and 5 of distinct amino acid and nucleotide compositions. Finally, introduction of preferred sequence motifs only at specific codon positions improves protein synthesis efficiency for recombinant proteins. Collectively, our data underscore the critical role of early elongation events in translational control of gene expression.

Inferring Gene-Species Assignments in the Presence of Horizontal Gene Transfer.

BACKGROUND: Microbial communities from environmental samples show great diversity as bacteria quickly responds to changes in their ecosystems. To assess the scenario of the actual changes, metagenomics experiments aimed at sequencing genomic DNA from such samples are performed. These new obtained sequences together with already known are used to infer phylogenetic trees assessing the taxonomic groups the species with these genes belong to. Here, we propose the first approach to the gene-species assignment problem by using reconciliation with horizontal gene transfer. RESULTS: We propose efficient algorithms that search for optimal gene-species mappings taking into account gene duplication, loss and transfer events under two tractable models of HGT reconciliation. CONCLUSIONS: We calculate both the optimal cost and all possible optimal scenarios. Furthermore as the number of optimal reconstructions can be large, we use a Monte-Carlo method for the inference of approximate distributions of gene-species assignments. We demonstrate the applicability on empirical and simulated datasets.

A conserved glycine residue of trimeric autotransporter domains plays a key role in Yersinia adhesin A autotransport.

The Yersinia adhesin A (YadA) is a trimeric autotransporter adhesin of enteric yersiniae. It consists of three major domains: a head mediating adherence to host cells, a stalk involved in serum resistance, and an anchor that forms a membrane pore and is responsible for the autotransport function. The anchor contains a glycine residue, nearly invariant throughout trimeric autotransporter adhesins, that faces the pore lumen. To address the role of this glycine, we replaced it with polar amino acids of increasing side chain size and expressed wild-type and mutant YadA in Escherichia coli. The mutations did not impair the YadA-mediated adhesion to collagen and to host cells or the host cell cytokine production, but they decreased the expression levels and stability of YadA trimers with increasing side chain size. Likewise, autoagglutination and resistance to serum were decreased in these mutants. We found that the periplasmic protease DegP is involved in the degradation of YadA and that in an E. coli degP deletion strain, mutant versions of YadA were expressed almost to wild-type levels. We conclude that the conserved glycine residue affects both the export and the stability of YadA and consequently some of its putative functions in pathogenesis.