Molecular aspects of the interaction between Mason-Pfizer monkey virus matrix protein and artificial phospholipid membrane.

The Mason-Pfizer monkey virus is a type D retrovirus, which assembles its immature particles in the cytoplasm prior to their transport to the host cell membrane. The association with the membrane is mediated by the N-terminally myristoylated matrix protein. To reveal the role of particular residues which are involved in the capsid-membrane interaction, covalent labelling of arginine, lysine and tyrosine residues of the Mason-Pfizer monkey virus matrix protein bound to artificial liposomes containing 95% of phosphatidylcholine and 5% phosphatidylinositol-(4,5)-bisphosphate (PI(4,5)P2 ) was performed. The experimental results were interpreted by multiscale molecular dynamics simulations. The application of these two complementary approaches helped us to reveal that matrix protein specifically recognizes the PI(4,5)P2 molecule by the residues K20, K25, K27, K74, and Y28, while the residues K92 and K93 stabilizes the matrix protein orientation on the membrane by the interaction with another PI(4,5)P2 molecule. Residues K33, K39, K54, Y66, Y67, and K87 appear to be involved in the matrix protein oligomerization. All arginine residues remained accessible during the interaction with liposomes which indicates that they neither contribute to the interaction with membrane nor are involved in protein oligomerization. Proteins 2016; 84:1717-1727. © 2016 Wiley Periodicals, Inc.

Occurrence of Cronobacter spp. in retail foods.

AIMS: To study the occurrence of Cronobacter spp. in foods and to investigate the phenotypic properties of the strains isolated. METHODS AND RESULTS: A total of 53 strains of Cronobacter spp. isolated from 399 food samples were identified using conventional biochemical methods and MALDI-TOF mass spectrometry. Foods of plant origin were the most frequently contaminated samples. No Cronobacter spp. were found in infant milk formula, wheat-based infant food, pasteurized and raw cow milk, mincemeat, chicken, chickpea and potato dumpling powder. The individual species were identified as Cronobacter sakazakii (54·7%), Cronobacter malonaticus (28·4%), Cronobacter dublinensis (7·5%), Cronobacter muytjensii (7·5%) and Cronobacter turicensis (1·9%). Cronobacter sakazakii and C. malonaticus belong to biotype 1, 2, 2a, 3, 4 and 5, 5a, respectively. Cronobacter dublinensis strains were subdivided into biotypes 6 and 12. All strains were resistant to erythromycin and two of them were resistant to both erythromycin and tetracycline. CONCLUSIONS: Cronobacter spp. were isolated from various food samples pre-eminently of plant origin and dried food ingredients. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings will increase and detail our knowledge of the presence and diversity of Cronobacter spp. in foods.

A high-density SNP genome-wide linkage scan in a large autism extended pedigree.

We performed a high-density, single nucleotide polymorphism (SNP), genome-wide scan on a six-generation pedigree from Utah with seven affected males, diagnosed with autism spectrum disorder. Using a two-stage linkage design, we first performed a nonparametric analysis on the entire genome using a 10K SNP chip to identify potential regions of interest. To confirm potentially interesting regions, we eliminated SNPs in high linkage disequilibrium (LD) using a principal components analysis (PCA) method and repeated the linkage results. Three regions met genome-wide significance criteria after controlling for LD: 3q13.2-q13.31 (nonparametric linkage (NPL), 5.58), 3q26.31-q27.3 (NPL, 4.85) and 20q11.21-q13.12 (NPL, 5.56). Two regions met suggestive criteria for significance 7p14.1-p11.22 (NPL, 3.18) and 9p24.3 (NPL, 3.44). All five chromosomal regions are consistent with other published findings. Haplotype sharing results showed that five of the affected subjects shared more than a single chromosomal region of interest with other affected subjects. Although no common autism susceptibility genes were found for all seven autism cases, these results suggest that multiple genetic loci within these regions may contribute to the autism phenotype in this family, and further follow-up of these chromosomal regions is warranted.

Kinetic modelling and meta-analysis of the B. subtilis SigA regulatory network during spore germination and outgrowth.

This study describes the meta-analysis and kinetic modelling of gene expression control by sigma factor SigA of Bacillus subtilis during germination and outgrowth based on microarray data from 14 time points. The analysis computationally models the direct interaction among SigA, SigA-controlled sigma factor genes (sigM, sigH, sigD, sigX), and their target genes. Of the >800 known genes in the SigA regulon, as extracted from databases, 311 genes were analysed, and 190 were confirmed by the kinetic model as being controlled by SigA. For the remaining genes, alternative regulators satisfying kinetic constraints were suggested. The kinetic analysis suggested another 214 genes as potential SigA targets. The modelling was able to (i) create a particular SigA-controlled gene expression network that is active under the conditions for which the expression time series was obtained, and where SigA is the dominant regulator, (ii) suggest new potential SigA target genes, and (iii) find other possible regulators of a given gene or suggest a new mechanism of its control by identifying a matching profile of unknown regulator(s). Selected predicted regulatory interactions were experimentally tested, thus validating the model.

Structure and expression of elongation factor Tu from Bacillus stearothermophilus.

The tuf gene coding for elongation factor Tu (EF-Tu) of Bacillus stearothermophilus was cloned and sequenced. This gene maps in the same context as the tufA gene of Escherichia coli str operon. Northern-blot analysis and primer extension experiments revealed that the transcription of the tuf gene is driven from two promoter regions. One of these is responsible for producing a 4.9-kb transcript containing all the genes of B. stearothermophilus str operon and the other, identified adjacent to the stop codon of the fus gene and designated tufp, for producing a 1.3-kb transcript of the tuf gene only. In contrast to the situation in E. coli, the ratio between the transcription products was found to be about 10:1 in favour of the tuf gene transcript. This high transcription activity from the tufp promoter might be accounted for by the presence of an extremely A+T-rich block consisting of 29 nucleotides which immediately precedes the consensus -35 region of the promoter. A very similar tuf gene transcription strategy and the same tufp promoter organization with the identical A/T block were found in Bacillus subtilis. The tuf gene specifies a protein of 395 amino acid residues with a molecular mass of 43,290 Da, including the N-terminal methionine. A computer-generated three-dimensional homology model shows that all the structural elements essential for binding guanine nucleotides and aminoacyl-tRNA are conserved. The presence of serine at position 376 and a low affinity for kirromycin determined by zone-interference gel electrophoresis (Kd approximately 8 microM) and by polyacrylamide gel electrophoresis under non-denaturing conditions are in agreement with the reported resistance of this EF-Tu to the antibiotic. The replacement of the highly conserved Leu211 by Met was identified as a possible cause of pulvomycin resistance.

Effect of host bacteria genotype on spontaneous reversions of Bacillus subtilis bacteriophage phi29 sus17 nonsense codon.

Gene 17 of Bacillus subtilis bacteriophage Phi29 is an early gene playing a role in DNA replication. Its mutant sus17(112) carries the TAA nonsense triplet at the fifth codon of the gene. We isolated and sequenced 73 spontaneous revertants producing normal-size plaques on bacteria without an informational suppressor gene. In all revertants, the TAA triplet was changed by a one-base substitution and the sequences CAA, AAA, TTA, TAC and TAT were recovered at its place. The spectrum of these mutations was markedly influenced by the genotype of the bacteria in which the revertants arose. In agreement with the results described in Escherichia coli, the ratio of transversions to transitions (CAA being the only transition acceptable) was higher in strains harboring the functional allele recA(+) than in those with recA4. Our results support the idea that also in the Gram-positive B. subtilis, the spectra of spontaneous mutations are specifically modified by an SOS function. It is assumed that the single-stranded DNA chains generated in the course of phage DNA replication might act as an inducing factor.

The pyrAb gene coding for the large subunit of carbamoylphosphate synthetase from Bacillus stearothermophilus: molecular cloning and functional characterization.

The Bacillus stearothermophilus pyrAb gene, encoding the large subunit of carbamoylphosphate synthetase, was isolated and characterized. The DNA sequence is a 3195-nucleotide long reading frame coding for a polypeptide of 1064 amino acids and deduced Mr approximately 116,160 Da. The pyrAb gene is part of the B. stearothermophilus pyrimidine biosynthesis operon pyr. The 5' end of thepyrAb gene overlaps with the 3' end of the pyrAa gene coding for the small subunit of carbamoylphosphate synthetase, while the 3' end of the pyrAb gene is overlapped with the 5' end of the pyrD gene, which by analogy with the B. subtilis genomic organization, codes for dihydroorotate dehydrogenase. The deduced amino acid sequence of the large subunit of B. stearothermophilus carbamoylphosphate synthetase was compared with the known sequences of the large subunit of carbamoylphosphate synthetase enzymes from other organisms via the NCBI database. Extremely high (98%) identity in amino acid sequence with the large subunit of carbamoylphosphate synthetase from Bacillus caldolyticus was detected.

Osmotin, a pathogenesis-related protein.

Plants protect themselves from pathogen invasion through the local expression of a variety of pathogenesis-related proteins. They are highly diverse in both primary structure and length, and exhibit different direct antimicrobial activity. This text reviews the knowledge of osmotin, antimicrobial protein involved in innate immunity of plants. Osmotin belongs to the fifth class of the group of pathogenesis-related (PR) proteins and has been found in different plants species, in every case osmotin is cysteine-rich protein involved in plant defense responses to several pathogens and abiotic stresses. The phylogenetic tree of amino acids compositions of osmotins from different plant species is presented and the basic similarities of clusters are discussed in this review. Osmotin gene is activated by different biotic as well as abiotic signals and has many functions. The review summarizes biochemical and structural properties, induction, functions and structural homology between osmotin and other proteins. Recent data about recombinant production in bacterial and plant cells are examined. The article indicates possible ways of osmotin application in research in the field of functional biology, medicine and agriculture.

Human melanoma cells expressing the alphavbeta3 integrin are partially protected from necrotic cell death induced by dynamic matrix detachment.

Anchorage-independence is a hallmark of metastatic cancer cells. In previous studies we characterized a novel model for anchorage-independence employing dynamic matrix detachment (DMD) using rotation in low shear stress conditions. We observed that in contrast to the classical apoptosis-inducing static matrix detachment (SMD) model, the venous circulation-mimicking DMD model induced necrosis in transformed cells. In the current study we revisited the mechanism of DMD-induced cell death and evaluated the contribution of alphavbeta3 integrin overexpression in human melanoma cells to anchorage-independence in DMD. DMD cell culture induced primarily necrosis in the melanoma cells studied. alphavbeta3, but not the control related alphaIIbbeta3 integrin, could confer survival advantage in DMD. While apoptosis was unaffected, constitutive, unligated alphavbeta3 overexpression was associated with attenuation of necrosis in DMD. alphavbeta3 overexpressing melanoma cells manifested AKT activation that was independent of DMD conditions. Furthermore, while a small molecular inhibitor of AKT phosphorylation induced apoptosis in adherent cells, in DMD conditions it had no effect on cell outcome. Thus, alphavbeta3-overexpressing melanoma cells are partially protected from DMD-induced cell death in an apoptosis-independent mechanism. This finding may be one of the factors accounting for anchorage-independence in circulating metastatic melanoma cells.

Cloning and characterization of the str operon and elongation factor Tu expression in Bacillus stearothermophilus.

The complete primary structure of the str operon of Bacillus stearothermophilus was determined. It was established that the operon is a five-gene transcriptional unit: 5'-ybxF (unknown function; homology to eukaryotic ribosomal protein L30)-rpsL (S12)-rpsG (S7)-fus (elongation factor G [EF-G])-tuf (elongation factor Tu [EF-Tu])-3'. The main operon promoter (strp) was mapped upstream of ybxF, and its strength was compared with the strength of the tuf-specific promoter (tufp) located in the fus-tuf intergenic region. The strength of the tufp region to initiate transcription is about 20-fold higher than that of the strp region, as determined in chloramphenicol acetyltransferase assays. Deletion mapping experiments revealed that the different strengths of the promoters are the consequence of a combined effect of oppositely acting cis elements, identified upstream of strp (an inhibitory region) and tufp (a stimulatory A/T-rich block). Our results suggest that the oppositely adjusted core promoters significantly contribute to the differential expression of the str operon genes, as monitored by the expression of EF-Tu and EF-G.

Subunit interaction in cyclic AMP-dependent protein kinase of mutant lymphoma cells.

We have previously selected and characterized mutant S49 mouse lymphoma cells that possess an adenosine 3':5'-cyclic monophosphate (cAMP)-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) with an increased apparent affinity constant (Ka) for activation by cAMP. The Ka lesion in one such mutant clone has been shown to result from a structural mutation involving the kinase holoenzyme's regulatory (R) subunit. The present report examines the interaction of R and catalytic (C) subunits of the kinases in extracts of the mutant cells and the normal "wild type" (WT) parental line. Subunit recombination experiments were performed, by using purified WT and mutant R subunits, and C subunits purified from WT cells. As compared to WT R subunits, only 1/6 as much mutant R subunit was required to reassociate with and suppress 50% of C subunit activity, at equilibrium. NaSCN activates cAMP-dependent kinase of both cell types by causing the holoenzyme to dissociate. In comparison with WT, a 2-fold higher concentration of NaSCN is required to maximally activate the kinase in mutant extracts. Both the reassociation result and the increased resistance of the mutant enzyme to a nonspecific dissociating agent strongly suggest that the mutant R subunit binds C subunit more tightly than does the WT R subunit. This interpretation raises the possibility that increased R-C subunit binding affinity in the mutant cell is responsible for the increased Ka for activation by cAMP of the mutant holoenzyme, and thus for the decreased potency of cAMP in regulating intact mutant cells.