Biomolecule-based antibacterial coating on a stainless steel surface: multilayer film build-up optimization and stability study.

The goal of this paper was to establish the durability profile of antibacterial multilayer thin films under storage and usage conditions. Thin films were built on stainless steel (SS) by means of a layer-by-layer process alternating a negatively charged polyelectrolyte, polyacrylic acid, with a cationic antibacterial peptide, nisin. SS coupons coated with the antibacterial film were challenged under environmental and usage conditions likely to be encountered in real-world applications. The change in antibacterial activity elicited by the challenge was used as an indicator of multilayer film resistance. Antibacterial SS samples could be stored for several weeks at 4°C in ambient air and antibacterial films were resistant to dipping and mild wiping in water and neutral detergent. The multilayer coating showed some weaknesses, however, that need to be addressed.

A green and bio-inspired process to afford durable anti-biofilm properties to stainless steel.

A bio-inspired durable anti-biofilm coating was developed for industrial stainless steel (SS) surfaces. Two polymers inspired from the adhesive and cross-linking properties of mussels were designed and assembled from aqueous solutions onto SS surfaces to afford durable coatings. Trypsin, a commercially available broad spectrum serine protease, was grafted as the final active layer of the coating. Its proteolytic activity after long immersion periods was demonstrated against several substrata, viz. a synthetic molecule, N-α-benzoyl-DL-arginine-p-nitroanilide hydrochloride (BAPNA), a protein, FTC-casein, and Gram-positive biofilm forming bacterium Staphylococcus epidermidis.

Nkx6.1 and nkx6.2 regulate alpha- and beta-cell formation in zebrafish by acting on pancreatic endocrine progenitor cells.

In mice, the Nkx6 genes are crucial to alpha- and beta-cell differentiation, but the molecular mechanisms by which they regulate pancreatic subtype specification remain elusive. Here it is shown that in zebrafish, nkx6.1 and nkx6.2 are co-expressed at early stages in the first pancreatic endocrine progenitors, but that their expression domains gradually segregate into different layers, nkx6.1 being expressed ventrally with respect to the forming islet while nkx6.2 is expressed mainly in beta-cells. Knockdown of nkx6.2 or nkx6.1 expression leads to nearly complete loss of alpha-cells but has no effect on beta-, delta-, or epsilon-cells. In contrast, nkx6.1/nkx6.2 double knockdown leads additionally to a drastic reduction of beta-cells. Synergy between the effects of nkx6.1 and nkx6.2 knockdown on both beta- and alpha-cell differentiation suggests that nkx6.1 and nkx6.2 have the same biological activity, the required total nkx6 threshold being higher for alpha-cell than for beta-cell differentiation. Finally, we demonstrate that the nkx6 act on the establishment of the pancreatic endocrine progenitor pool whose size is correlated with the total nkx6 expression level. On the basis of our data, we propose a model in which nkx6.1 and nkx6.2, by allowing the establishment of the endocrine progenitor pool, control alpha- and beta-cell differentiation.

Biomolecules in multilayer film for antimicrobial and easy-cleaning stainless steel surface applications.

Microorganisms are able to attach to, grow on, and ultimately form biofilms on a large variety of surfaces, such as industrial equipment, food contact surfaces, medical implants, prostheses and operating rooms. Once organized into biofilms, bacteria are difficult to remove and kill, which increases the risk of cross-contamination and infection. One way to address the problem may thus be to develop antibacterial, anti-adhesion, 'easy cleaning' surfaces. In this study, stainless steel (SS) surfaces with antibacterial properties were created by embedding several antimicrobial peptides in a multilayer film architecture. The biocidal effect of these surfaces was demonstrated against both Gram-positive and Gram-negative bacteria according to two ISO tests. Also, coating SS surfaces with either mucin or heparin led to a reduction of S. epidermidis adhesion of almost 95% vs the bare substratum. Finally, by combining both antibacterial and anti-adhesion biomolecules in the same multilayer film, SS surfaces with better cleanability were produced. This surface coating property may help to delay the buildup of a dead bacterial layer which is known to progressively reduce exposure of the coating, leading to an undesirable decrease in the antibacterial effect of the surface.

Cell-free synthesis of acetylcholine receptor polypeptides.

Messenger RNA coding for acetylcholine receptor peptides has been identified. This polyadenylate [poly(A)+]RNA from Torpedo californica directs, in a cell-free system, the synthesis of peptides 60,000, 51,000, 49,000 41,000, and 35,000 daltons which account for approximately 2 percent of the total synthesized proteins. The results suggest that several different messenger RNA's code for the receptor subunits. These proteins react specifically to antiserum to native acteylcholine receptor, suggesting that the primary translational product has conformational features similar to the native receptor. Further, the results support the idea that there is post-translational modification of receptor subunits as the molecular weights of the cell-free synthesized proteins differ from those of purified receptor subunits.

Human growth hormone: complementary DNA cloning and expression in bacteria.

The nucleotide sequence of a DNA complementary to human growth hormone messenger RNA was cloned; it contains 29 nucleotides in its 5' untranslated region, the 651 nucleotides coding for the prehormone, and the entire 3' untranslated region (108 nucleotides). The data reported predict the previously unknown sequence of the signal peptide of human growth hormone and, by comparison with the previously determined sequences of rat growth hormone and human chorionic somatomammotropin, strengthens the hypothesis that these genes evolved by gene duplication from a common ancestral sequence. The human growth hormone gene sequences have been linked in phase to a fragment of the trp D gene of Escherichia coli in a plasmid vehicle, and a fusion protein is synthesized at high level (approximately 3 percent of bacterial protein) under the control of the regulatory region of the trp operon. This fusion protein (70 percent of whose amino acids are coded for by the human growth hormone gene) reacts specifically with antibodies to human growth hormone and is stable in E. coli.

The prolactin gene is located on chromosome 6 in humans.

The gene for prolactin has been located on chromosome 6 in humans. DNA fragments of 4.8 and 4.0 kilobases containing prolactin gene sequences were identified in human genomic DNA, whereas DNA fragments of 7.4, 3.6, and 3.3 kilobases containing prolactin gene sequences were found in mouse cells. In somatic cell hybrids of human and mouse cells the 7.4-, 3.6-, and 3.3-kilobase mouse fragments were always present, whereas the 4.8- and 4.0-kilobase human fragments were only present when human chromosome 6 was also present. We conclude that the prolactin gene resides on chromosome 6, a different location from those of the genes for the related hormones chorionic somatomammotropin and growth hormone.

Genes for growth hormone, chorionic somatommammotropin, and growth hormones-like gene on chromosome 17 in humans.

The human genes for growth hormone (GH), chorionic somatomammotropin (CSH), and a third growth hormone-like gene (GHL) have been located on chromosome 17 in humans. DNA fragments of 2.6, 2.8, and 9.5 kilobase pairs containing GH, CSH, and GHL, respectively, were identified in human genomic DNA, and a 7.5-kilobase DNA fragment related to growth hormone DNA sequences was found in mouse cells. In somatic hybrids of human and mouse cells containing reduced numbers of human chromosomes, but a normal complement of mouse chromosomes, the mouse, 7.5-kolobase DNA fragment was always present, whereas the 2.6-, 2.8-, and 9.5-kilobase human fragments were present only when human chromosome 17 was also present.

Thyroid hormonelike actions of 3,3',5'-L-triiodothyronine nad 3,3'-diiodothyronine.

l-Thyroxine is converted to 3,5,3'-l-triiodothyronine (T(3)) as well as to 3,3',5'-l-triiodothyronine (reverse T(3)). One product of further deiodination is 3,3'-diiodothyronine (3,3'T(2)). The serum levels of reverse T(3) and 3,3'T(2) change considerably in various physiological and disease states. We previously found that reverse T(3) and 3,3'T(2) bind to the solubilized hepatic nuclear "receptors" for thyroid hormones. This led us to study binding and actions of these metabolites in cultured rat pituitary cells in which glucose consumption and growth hormone production are regulated by T(3) and l-thyroxine. Reverse T(3) and 3,3'T(2) stimulated growth hormone production and glucose consumption and inhibited nuclear binding of radioactive T(3). Either metabolite produced maximal effects that equaled those of T(3), and neither inhibited the T(3) response. Further, additive effects were observed when reverse T(3) was combined with submaximal concentrations of T(3). In serum-free and serum-containing media, concentrations of 3,3'T(2) 50- to 70- and 10- to 100-fold greater, respectively, than those of T(3) were required for equivalent stimulations and for inhibition of nuclear binding by T(3). The relative activity differences under the two conditions can be attributed to weaker serum protein binding of 3,3'T(2) than T(3). With cells in serum-free media, reverse T(3) was a less avid competitor than 3,3'T(2) for T(3) binding by the nuclear receptors, and was less potent than 3,3'T(2) (0.001 the potency of T(3)) in inducing growth hormone production or glucose oxidation. In incubations with serum-containing media, reverse T(3) was an ineffective competitor for T(3) binding, and had only 0.1 the inducing potency of 3,3'T(2) (0.001 the potency of T(3)). The weaker activity of reverse T(3) relative to 3,3'T(2) in serum-containing media could be explained by stronger serum binding of reverse T(3) than 3,3'T(2). In addition, after long-term incubation of cells with radioactive reverse T(3), much of the cell-associated radioactivity was recovered as 3,3'T(2). These studies suggest that reverse T(3) and 3,3'T(2) can stimulate thyroid hormone-regulated functions as weak agonists by acting via the same receptors that mediate T(3) actions. Moreover, some of the effects of reverse T(3) may be due to 3,3'T(2) produced by deiodination of reverse T(3).

Prolactin-deficient variants of GH3 rat pituitary tumor cells: linked expression of prolactin and another hormonally responsive protein in GH3 cells.

GH3 cells normally synthesize and secrete two pituitary polypeptide hormones, prolactin and growth hormone. From an ethyl methane sulfonate-mutagenized population, prolactin low-producing variants have been isolated at a frequency near 20%. Intracellular prolactin synthesis in the variants was reduced 40- to 100-fold compared to wild-type cells while growth hormone synthesis varied less than 2-fold. This decrease was paralleled by a decrease in intracellular preprolactin mRNA. Although reduced, prolactin synthesis was still repressible by glucocorticoids. There was a coordinate loss of expression of p21, a thyroid and glucocorticoid hormone-regulated protein, in GH3 cells, whereas the synthesis and regulation of other hormonally responsive proteins were unimpaired in the variants. Since p21 expression was coordinately regained in a high-producing prolactin revertant cell, expression of the two proteins is tightly coupled in GH3 cells. The stability of the low-producing phenotype differed among variants. One (B2) gave rise to revertants at about 20% frequency even after two rounds of subcloning, whereas another (B3) was more stable in that only 1 weak revertant was found in 47 subclones. The reversion frequency of B3 cells was also measured at less than 0.5%. Unmutagenized GH3 cells were phenotypically stable in that no prolactin-deficient variant was found among 57 subclones. Since variants were ony found after ethyl methane sulfonate mutagenesis, the DNA alkylating agent appears to have promoted an epigenetic change in pituitary gene expression.

Characterization of a single strong tissue-specific enhancer downstream from the three human genes encoding placental lactogen.

The human genes coding for growth hormone (hGH) and placental lactogen (choriosomatomammotropic hormone [hCS]) are clustered on chromosome 17 in the following order: 5' hGH-N hCS-L hCS-A hGH-V hCS-B 3'. So far, a single placenta-specific enhancer has been identified in the locus, 2 kb downstream from the hCS-B gene, and shown to comprise one in vitro binding site for a nuclear protein. We here provide evidence that the hCS-B enhancer is more complex: (i) protection against DNase I digestion in the 3' flanking region of the hCS-B gene reveals four binding sites (DF-1, DF-2, DF-3, and DF-4) for nuclear proteins from either placental or HeLa cells, and (ii) placenta-specific enhancer activity can be fully exerted in transient expression experiments by a 126-bp fragment comprising the DF-3 and DF-4 protein-binding sites. By dissecting this region, we show that enhancer activity is mediated by a synergy between DF-3 and DF-4. Competitions with various oligonucleotides in footprinting and gel retardation experiments indicate that the same protein or set of proteins, different in HeLa and placenta cell nuclei, interacts with sites DF-2, DF-3, and DF-4. We also studied the regions of the hCS-L and hCS-A genes which are highly similar to the hCS-B enhancer. Although they each present the same four protein-binding sites, they exhibit only minor enhancer activity.

Regulatory elements controlling pituitary-specific expression of the human prolactin gene.

We have performed transfection and DNase I footprinting experiments to investigate pituitary-specific expression of the human prolactin (hPRL) gene. When fused to the chloramphenicol acetyltransferase (CAT) reporter gene, 5,000 base pairs of the 5'-flanking sequences of the hPRL gene were able to drive high cat gene expression in prolactin-expressing GH3B6 cells specifically. Deletion analysis indicated that this pituitary-specific expression was controlled by three main positive regulatory regions. The first was located just upstream from the TATA box between coordinates -40 and -250 (proximal region). We have previously shown that three motifs of this region bind the pituitary-specific Pit-1 factor. The second positive region was located in the vicinity of coordinates -1300 to -1750 (distal region). DNase I footprinting assays revealed that eight DNA motifs of this distal region bound protein Pit-1 and that two other motifs were recognized by ubiquitous factors, one of which seems to belong to the AP-1 (jun) family. The third positive region was located further upstream, between -3500 and -5000 (superdistal region). This region appears to enhance transcription only in the presence of the distal region.

Transcriptional regulation by triiodothyronine requires synergistic action of the thyroid receptor with another trans-acting factor.

Human placental lactogen B (hCS-B) promoter activity is strongly stimulated by triiodothyronine (T3) in pituitary GC cells through interaction between the thyroid receptor and a thyroid receptor-binding element (TBE) spanning coordinates -67 to -41. This TBE is adjacent to the binding site for pituitary factor GHF1 (-95 to -68) which seems necessary for T3 stimulation of hCS-B promoter activity (M. L. Voz, B. Peers, A. Belayew, and J. A. Martial, J. Biol. Chem. 266:13397-13404, 1991). We here demonstrate actual synergy between the thyroid receptor and GHF1. Indeed, in placental JEG-3 cells devoid of factor GHF1, hCS promoter activity is barely stimulated by T3, while a strong response is observed in pituitary GC cells. In the latter, furthermore, neither the TBE nor the GHF1-binding site alone is sufficient to render the thymidine kinase promoter responsive to T3, while in combination they promote strong T3 stimulation. Close proximity between these sites is required for optimal synergy: T3 stimulation globally decreases with increased spacing. Furthermore, synergy occurs not only with a GHF1-binding site but also with all other factor recognition sequences tested (Sp1, NF1, CP1, Oct1, and CACCC boxes) and even with two other copies of the TBE. Nor is it specific to hCS TBE, since the palindromic sequence TCAGGTCA TGACCTGA (TREpal) also exhibits cooperativity.

The ornithine decarboxylase gene is essential for cell survival during early murine development.

Overexpression and inhibitor studies have suggested that the c-Myc target gene for ornithine decarboxylase (ODC), the enzyme which converts ornithine to putrescine, plays an important role in diverse biological processes, including cell growth, differentiation, transformation, and apoptosis. To explore the physiological function of ODC in mammalian development, we generated mice harboring a disrupted ODC gene. ODC-heterozygous mice were viable, normal, and fertile. Although zygotic ODC is expressed throughout the embryo prior to implantation, loss of ODC did not block normal development to the blastocyst stage. Embryonic day E3.5 ODC-deficient embryos were capable of uterine implantation and induced maternal decidualization yet failed to develop substantially thereafter. Surprisingly, analysis of ODC-deficient blastocysts suggests that loss of ODC does not affect cell growth per se but rather is required for survival of the pluripotent cells of the inner cell mass. Therefore, ODC plays an essential role in murine development, and proper homeostasis of polyamine pools appears to be required for cell survival prior to gastrulation.

Expression of the antiangiogenic factor 16K hPRL in human HCT116 colon cancer cells inhibits tumor growth in Rag1(-/-) mice.

The M(r) 16,000 NH(2)-terminal fragment of human prolactin (16K hPRL) is a potent antiangiogenic factor inhibiting endothelial cell function in vitro and neovascularization in vivo. The present study was undertaken to test the ability of 16K hPRL to inhibit the growth of human HCT116 colon cancer cells transplanted s.c. into Rag1(-/-) mice. For this purpose, HCT116 cells were stably transfected with an expression vector encoding a peptide that included the signal peptide and first 139 amino acid residues of human prolactin (HCT116(16K)). Stable clones of HCT116(16K) cells secreted large amounts of biologically active 16K hPRL into the culture medium. Growth of HCT116(16K) cells in vitro was not different from wild-type HCT116 (HCT116(wt)) or vector-transfected HCT116 (HCT116(vector)) cells. Addition of recombinant 16K hPRL had no effect on the proliferation of HCT116(wt) cells in vitro. Tumor growth of HCT116(16K) cells implanted into Rag1(-/-) mice was inhibited 63% in four separate experiments compared with tumors formed from HCT116(wt) or HCT116(vector) cells. Inhibition of tumor growth of HCT116(16K) cells was correlated with a decrease in microvascular density by 44%. These data demonstrate that biologically active 16K hPRL can be expressed and secreted from human colon cancer cells using a gene transfer approach and that production of 16K hPRL by these cells was capable of inhibiting tumor growth and neovascularization. These findings support the potential of 16K hPRL as a therapeutic agent for the treatment of colorectal cancer.

Gene structure and promoter function of a teleost ribosomal protein: a tilapia (Oreochromis mossambicus) L18 gene.

We have cloned and characterized a tilapia (Oreochromis mossambicus) L18 ribosomal protein gene, including the complete transcribed region and 488 bp of upstream regulatory sequences. We have also isolated two L18 cDNAs from another tilapia (Oreochromis niloticus) with a few conservative nucleotide differences. Our results suggest the presence of two genes in both species. Reporter constructs were tested for transient expression in CV1 cells and in microinjected zebrafish and tilapia embryos. The tilapia L18 promoter was able to drive expression of the reporter gene in all three experiments, with no apparent preference for a particular tissue. The tilapia L18 promoter is therefore likely to be a powerful tool to drive tissue-independent gene expression in fish.

Kzf1 - a novel KRAB zinc finger protein encoding gene expressed during rat spermatogenesis.

Two novel KRAB (Krüppel associated box) type zinc finger protein encoding cDNAs, named Kzf1 and Kzf2 (Kzf for KRAB zinc finger), were identified by screening of a rat embryonic brain cDNA library with a human ZNF91 KRAB probe. Kzf1 and Kzf2 encode proteins with an amino-terminal KRAB domain and a carboxy-terminal zinc finger cluster containing 9 and 13 zinc finger units, respectively. While Kzf2 appears to be ubiquitously expressed, Kzf1 is preferentially expressed in the testis. Within the testis, Kzf1 mRNA is restricted to germ cells. The Kzf1 protein exhibits DNA binding activity and its KRAB domain can function as a repressor module in transcription. Using somatic cell hybrid analysis, the Kzf1 gene was mapped to chromosome 6.

Three hTIM mutants that provide new insights on why TIM is a dimer.

Human triosephosphate isomerase (hTIM), a dimeric enzyme, was altered by site-directed mutagenesis in order to determine whether it can be dissociated into monomers. Two hTIM mutants were produced, in which a glutamine residue was substituted for either Met14 or Arg98, both of which are interface residuces. These substitutions strongly interfere with TIM subunit association, since these mutant TIMs appear to exist as compact monomers in dynamic equilibrium with dimers. In kinetic studies, the M14Q mutant exhibits significant catalytic activity, while the R98Q enzyme is inactive. The M14Q enzyme is nevertheless much less active than unmutated hTIM. Moreover, its specific activity is concentration dependent, suggesting a dissociation process in which the monomers are inactive. In order to determine the conformational stability of the wild-type and mutant hTIMs, unfolding of all three enzymes was monitored by circular dichroism and tryptophan fluorescence spectroscopy. In each case, protein stability is concentration dependent, and the unfolding reaction is compatible with a two-state model involving the native dimer and unfolded monomers. The conformational stability of hTIM, as estimated according to this model, is 19.3 (+/-0.4) kcal/mol. The M14Q and R98Q replacements significantly reduce enzyme stability, since the free energies of unfolding are 13.8 and 13.5 (+/- 0.3) kcal/mol respectively, for the mutants, A third mutant, in which the M14Q and R98Q replacements are cumulated, behaves like a monomer. The stability of this mutant is not concentration-dependent, and the unfolding reaction is assigned to a transition from a folded monomer to an unfolded monomer. The conformational stability of this double mutant is estimated 2.5 (+/-0.1) kcal/mol. All these data combined suggest that TIM monomers are thermodynamically unstable. This might explain why TIM occurs only as a dimer.

Cloning and overexpression of the triosephosphate isomerase genes from psychrophilic and thermophilic bacteria. Structural comparison of the predicted protein sequences.

We focused on the temperature adaptation of triosephosphate isomerase (TIM; E.C. 5.3.1.1.) by comparing the structure of TIMs isolated from bacterial organisms living in either cold or hot environments. The TIM gene from psychrophilic bacteria Moraxella sp. TA137 was cloned and its nucleotide sequence determined. Its deduced amino acid sequence revealed 34% identity with the thermophilic bacteria Bacillus stearothermophilus TIM. Expression vectors were constructed and recombinant Moraxella TA137 and Bacillus stearothermophilus TIMs were overproduced and purified to homogeneity. Recombinant TIM inactivation constants (Ki), measured at various temperatures, compared to those of the mesophilic Escherichia coli recombinant TIM clearly show that Moraxella TA137 and B. stearothermophilus TIMs have respectively psychrophilic and thermophilic characteristics. To try to elucidate the structure-thermolability and structure-thermostability relationship, factors affecting the overall stability of these two TIMs were examined, based on the alignment with the mesophilic chicken TIM, the three-dimensional structure of which is already known. From this comparison, it appears that the adaptability of TIM to high temperature is favored by better stabilizing residues for the helix dipole as well as better helix-forming residues whereas the adaptability of TIM to low temperature seems to reside in the nature of helix-capping residues.

De novo backbone and sequence design of an idealized alpha/beta-barrel protein: evidence of stable tertiary structure.

We have designed, synthesized, and characterized a 216 amino acid residue sequence encoding a putative idealized alpha/beta-barrel protein. The design was elaborated in two steps. First, the idealized backbone was defined with geometric parameters representing our target fold: a central eight parallel-stranded beta-sheet surrounded by eight parallel alpha-helices, connected together with short structural turns on both sides of the barrel. An automated sequence selection algorithm, based on the dead-end elimination theorem, was used to find the optimal amino acid sequence fitting the target structure. A synthetic gene coding for the designed sequence was constructed and the recombinant artificial protein was expressed in bacteria, purified and characterized. Far-UV CD spectra with prominent bands at 222nm and 208nm revealed the presence of alpha-helix secondary structures (50%) in fairly good agreement with the model. A pronounced absorption band in the near-UV CD region, arising from immobilized aromatic side-chains, showed that the artificial protein is folded in solution. Chemical unfolding monitored by tryptophan fluorescence revealed a conformational stability (DeltaG(H2O)) of 35kJ/mol. Thermal unfolding monitored by near-UV CD revealed a cooperative transition with an apparent T(m) of 65 degrees C. Moreover, the artificial protein did not exhibit any affinity for the hydrophobic fluorescent probe 1-anilinonaphthalene-8-sulfonic acid (ANS), providing additional evidence that the artificial barrel is not in the molten globule state, contrary to previously designed artificial alpha/beta-barrels. Finally, 1H NMR spectra of the folded and unfolded proteins provided evidence for specific interactions in the folded protein. Taken together, the results indicate that the de novo designed alpha/beta-barrel protein adopts a stable three-dimensional structure in solution. These encouraging results show that de novo design of an idealized protein structure of more than 200 amino acid residues is now possible, from construction of a particular backbone conformation to determination of an amino acid sequence with an automated sequence selection algorithm.