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Molecular characterization of enterobacterial pldA genes encoding outer membrane phospholipase A.

ABSTRACT: The pldA gene of Escherichia coli encodes an outer membrane phospholipase A. A strain carrying the most commonly used mutant pldA allele appeared to express a correctly assembled PldA protein in the outer membrane. Nucleotide sequence analysis revealed that the only difference between the wild type and the mutant is the replacement of the serine residue in position 152 by phenylalanine. Since mutants that lack the pldA gene were normally viable under laboratory conditions and had no apparent phenotype except for the lack of outer membrane phospholipase activity, the exact role of the enzyme remains unknown. Nevertheless, the enzyme seems to be important for the bacteria, since Western blotting (immunoblotting) and enzyme assays showed that it is widely spread among species of the family Enterobacteriaceae. To characterize the PldA protein further, the pldA genes of Salmonella typhimurium, Klebsiella pneumoniae, and Proteus vulgaris were cloned and sequenced. The cloned genes were expressed in E. coli, and their gene products were enzymatically active. Comparison of the predicted PldA primary structures with that of E. coli PldA revealed a high degree of homology, with 79% of the amino acid residues being identical in all four proteins. Implications of the sequence comparison for the structure and the structure-function relationship of PldA protein are discussed.

SUBMITTER: Brok RG

PROVIDER: S-EPMC205124 | biostudies-other | 1994 Feb

REPOSITORIES: biostudies-other

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Molecular characterization of enterobacterial pldA genes encoding outer membrane phospholipase A.

Brok R G RG Brinkman E E van Boxtel R R Bekkers A C AC Verheij H M HM Tommassen J J

Journal of bacteriology 19940201 3

The pldA gene of Escherichia coli encodes an outer membrane phospholipase A. A strain carrying the most commonly used mutant pldA allele appeared to express a correctly assembled PldA protein in the outer membrane. Nucleotide sequence analysis revealed that the only difference between the wild type and the mutant is the replacement of the serine residue in position 152 by phenylalanine. Since mutants that lack the pldA gene were normally viable under laboratory conditions and had no apparent phe ...[more]

PMID: 8300539

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Project description:In the past decade, researchers have proposed that the pldA gene for outer membrane phospholipase A (OMPLA) is important for bacterial colonization of the human gastric ventricle. Several conserved Helicobacter pylori genes have distinct genotypes in different parts of the world, biogeographic patterns that can be analyzed through phylogenetic trees. The current study will shed light on the importance of the pldA gene in H. pylori. In silico sequence analysis will be used to investigate whether the bacteria are in the process of preserving, optimizing, or rejecting the pldA gene. The pldA gene will be phylogenetically compared to other housekeeping (HK) genes, and a possible origin via horizontal gene transfer (HGT) will be evaluated through both intra- and inter-species evolutionary analyses.In this study, pldA gene sequences were phylogenetically analyzed and compared with a large reference set of concatenated HK gene sequences. A total of 246 pldA nucleotide sequences were used; 207 were from Norwegian isolates, 20 were from Korean isolates, and 19 were from the NCBI database. Best-fit evolutionary models were determined with MEGA5 ModelTest for the pldA (K80 + I + G) and HK (GTR + I + G) sequences, and maximum likelihood trees were constructed. Both HK and pldA genes showed biogeographic clustering. Horizontal gene transfer was inferred based on significantly different GC contents, the codon adaptation index, and a phylogenetic conflict between a tree of OMPLA protein sequences representing 171 species and a tree of the AtpA HK protein for 169 species. Although a vast majority of the residues in OMPLA were predicted to be under purifying selection, sites undergoing positive selection were also found.Our findings indicate that the pldA gene could have been more recently acquired than seven of the HK genes found in H. pylori. However, the common biogeographic patterns of both the HK and pldA sequences indicated that the transfer occurred long ago. Our results indicate that the bacterium is preserving the function of OMPLA, although some sites are still being evolutionarily optimized.

Dataset Information

Molecular characterization of enterobacterial pldA genes encoding outer membrane phospholipase A.

Publications

Molecular characterization of enterobacterial pldA genes encoding outer membrane phospholipase A.

Similar Datasets

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