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Structural Determinants Required To Target Penicillin-Binding Protein 3 to the Septum of Escherichia coli. André Piette, 2004.In Escherichia coli, cell division is mediated by the concerted action of about 12 proteins that assemble at the division site to presumably form a complex called the divisome . Among these essential division proteins, the multimodular class B penicillin-binding protein 3 [PBP3], which is specifically involved in septal peptidoglycan synthesis, consists of a short intracellular M1-R23 peptide fused to a F24-L39 membrane anchor that is linked via a G40-S70 peptide to an R71-I236 noncatalytic module itself linked toa D237-V577 catalytic penicillin-binding module . On the basisof localization analyses of PBP3 mutants fused to green fluorescent protein by fluorescence microscopy, it appears that the first56 amino acid residues of PBP3 containing the membrane anchorand the G40-E56 peptide contain the structural determinantsrequired to target the protein to the cell division site andthat none of the putative protein interaction sites presentin the noncatalytic module are essential for the positioningof the protein to the division site . Based on the effects ofincreasing production of FtsQ or FtsW on the division of cellsexpressing PBP3 mutants, it is suggested that these proteinscould interact . We postulate that FtsQ could play a role inregulating the assembly of these division proteins at the divisionsite and the activity of the peptidoglycan assembly machinerieswithin the divisome. Genomic DNA Microarray Analysis: Identification of New Genes Regulated by Light Color in the Cyanobacterium Fremyella diplosiphon. Emily L. Stowe-Evans, 2004.Many cyanobacteria use complementary chromatic adaptation to efficiently utilize energy from both green and red regions of the light spectrum during photosynthesis . Although previous studies have shown that acclimation to changing light wavelengths involves many physiological responses, research to date has focused primarily on the expression and regulation of genes that encode proteins of the major photosynthetic light-harvesting antennae, the phycobilisomes . We have used two-dimensional gel electrophoresis and genomic DNA microarrays to expand our understanding of the physiology of acclimation to light color in the cyanobacterium Fremyella diplosiphon . We found that the levels of nearly 80 proteins are altered in cells growing in green versus red light and have cloned and positively identified 17 genes not previously known to be regulated by light color in any species . Among these are homologs of genes present in many bacteria that encode well-studied proteins lacking clearly defined functions, such as tspO, which encodes a tryptophan-rich sensory protein, and homologs of genes encoding proteins of clearly defined function in many species, such as nblA and chlL, encoding phycobilisome degradation and chlorophyll biosynthesis proteins, respectively . Our results suggest novel roles for several of these gene products and highly specialized, unique uses for others . An Adenylyl Cyclase, CyaA, of Myxococcus xanthus Functions in Signal Transduction during Osmotic Stress. Yoshio Kimura, 2002.An adenylyl cyclase gene (cyaA) present upstream of an osmosensor protein gene (mokA) was isolated from Myxococcus xanthus . cyaA encoded a polypeptide of 843 amino acids with a predicted molecular mass of 91,187 Da . The predicted cyaA gene product had structural similarity to the receptor-type adenylyl cyclases that are composed of an amino-terminal sensor domain and a carboxy-terminal catalytic domain of adenylyl cyclase . In reverse transcriptase PCR experiments, the transcript of the cyaA gene was detected mainly during development and spore germination . A cyaA mutant, generated by gene disruption, showed normal growth, development, and germination . However, a cyaA mutant placed under conditions of ionic (NaCl) or nonionic (sucrose) osmostress exhibited a marked reduction in spore formation and spore germination . When wild-type and cyaA mutant cells at developmental stages were stimulated with 0.2 M NaCl or sucrose, the mutant cells increased cyclic AMP accumulation at levels similar to those of the wild-type cells . In contrast, the mutant cells during spore germination had mainly lost the ability to respond to high-ionic osmolarity . In vegetative cells, the cyaA mutant responded normally to osmotic stress . These results suggested that M . xanthus CyaA functions mainly as an ionic osmosensor during spore germination and that CyaA is also required for osmotic tolerance in fruiting formation and sporulation . Structural Heterogeneity of the Streptococcal C5a Peptidase Gene in Streptococcus pyogenes. Irina V. Koroleva, 2002.The 3' ends of the genes for the C-terminal region of C5a peptidase from 15 Streptococcus pyogenes isolates were analyzed by PCR . Amplicons were found to differ in size . DNA sequence analysis revealed that the differences between PCR fragment sizes accorded with the number of R repeats in the C5a peptidase gene . Molecular Analysis of the Copper-Transporting Efflux System CusCFBA of Escherichia coli. Sylvia Franke, 2003.The cus determinant of Escherichia coli encodes the CusCFBA proteins that mediate resistance to copper and silver by cation efflux . CusA and CusB were essential for copper resistance, and CusC and CusF were required for full resistance . Replacements of methionine residues 573, 623, and 672 with isoleucine in CusA resulted in loss of copper resistance, demonstrating their functional importance . Substitutions for several other methionine residues of this protein did not have any effect . The small 10-kDa protein CusF (previously YlcC) was shown to be a periplasmic protein . CusF bound one copper per polypeptide . The pink CusF copper protein complex exhibited an absorption maximum at around 510 nm . Methionine residues of CusF were involved in copper binding as shown by site-directed mutagenesis . CusF interacted with CusB and CusC polypeptides in a yeast two-hybrid assay . In contrast to other well-studied CBA-type heavy metal efflux systems, Cus was shown to be a tetrapartite resistance system that involves the novel periplasmic copper-binding protein CusF . These data provide additional evidence for the hypothesis that Cu(I) is directly transported from the periplasm across the outer membrane by the Cus complex .
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