Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent studies have shown that expression of the Staphylococcus aureus lrgAB operon inhibits murein hydrolase activity and decreases sensitivity to penicillin-induced killing. It was proposed that the lrgAB gene products function in a manner analogous to an antiholin, inhibiting a putative holin from transporting murein hydrolases out of the cell. In the present study the cidAB operon was identified and characterized based on the similarity of the cidA and cidB gene products to the products of the lrgAB operon. Zymographic and quantitative analyses of murein hydrolase activity revealed that mutation of the cidA gene results in decreased extracellular murein hydrolase activity compared to that of S. aureus RN6390, the parental strain. Complementation of cidA expression restored the wild-type phenotype, indicating that expression of the cidAB operon has a positive influence on extracellular murein hydrolase activity. The cidA mutant also displayed a significant decrease in sensitivity to the killing effects of penicillin. However, complementation of the cidA defect did not restore penicillin sensitivity to wild-type levels. Reverse transcriptase PCR also revealed that cidAB is maximally expressed during early exponential growth, opposite of what was previously observed for lrgAB expression. Based on these results, we propose that the cidAB operon encodes the holin-like counterpart of the lrgAB operon and acts in a manner opposite from that of lrgAB by increasing extracellular murein hydrolase activity and increasing sensitivity to penicillin-induced killing.
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PMID:The Staphylococcus aureus cidAB operon: evaluation of its role in regulation of murein hydrolase activity and penicillin tolerance. 1267 Sep 89

The yqiHIK gene cluster from Bacillus subtilis is predicted to encode an extracellular lipoprotein (YqiH), a secreted N-acetylmuramoyl-L-alanine amidase (YqiI), and a cytoplasmic glycerophosphodiester phosphodiesterase (YqiK). Reverse transcriptase PCR (RT-PCR) analysis showed that the yqiHIK genes are transcribed as an operon. Consistent with the in silico prediction, we found that the purified YqiI protein exhibited hydrolytic activity toward peptidoglycan sacculi. Transcription studies with yqiH-treA reporter fusion strains revealed that the expression of yqiHIK is subjected to finely tuned osmotic control, but enhanced expression occurs only in severely osmotically stressed cells. Primer extension analysis pinpointed the osmotically responsive yqiHIK promoter, and site-directed mutagenesis was employed to assess functionally important sequences required for promoter activity and osmotic control. Promoter variants with constitutive activity were isolated. A deletion analysis of the yqiHIK regulatory region showed that a 53-bp AT-rich DNA segment positioned 180 bp upstream of the -35 sequence is critical for the activity and osmotic regulation of the yqiHIK promoter. Hence, the expression of yqiHIK is subjected to genetic control at a distance. Upon the onset of growth of cells of the B. subtilis wild-type strain in high-salinity medium (1.2 M NaCl), we observed gross morphological deformations of cells that were then reversed to a rod-shaped morphology again when the cells had adjusted to the high-salinity environment. The products of the yqiHIK gene cluster were not critical for reestablishing rod-shaped morphology, but the deletion of this operon yielded a B. subtilis mutant impaired in growth in a defined minimal medium and at high salinity.
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PMID:Activity of the osmotically regulated yqiHIK promoter from Bacillus subtilis is controlled at a distance. 2284 46