Document Detail


MS_RHII-RSD, a dual-function RNase HII-(p)ppGpp synthetase from Mycobacterium smegmatis.
MedLine Citation:
PMID:  22636779     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
In the noninfectious soil saprophyte Mycobacterium smegmatis, intracellular levels of the stress alarmones guanosine tetraphosphate and guanosine pentaphosphate, together termed (p)ppGpp, are regulated by the enzyme Rel(Msm). This enzyme consists of a single, bifunctional polypeptide chain that is capable of both synthesizing and hydrolyzing (p)ppGpp. The rel(Msm) knockout strain of M. smegmatis (Δrel(Msm)) is expected to show a (p)ppGpp null [(p)ppGpp(0)] phenotype. Contrary to this expectation, the strain is capable of synthesizing (p)ppGpp in vivo. In this study, we identify and functionally characterize the open reading frame (ORF), MSMEG_5849, that encodes a second functional (p)ppGpp synthetase in M. smegmatis. In addition to (p)ppGpp synthesis, the 567-amino-acid-long protein encoded by this gene is capable of hydrolyzing RNA·DNA hybrids and bears similarity to the conventional RNase HII enzymes. We have classified this protein as actRel(Msm) in accordance with the recent nomenclature proposed and have named it MS_RHII-RSD, indicating the two enzymatic activities present [RHII, RNase HII domain, originally identified as domain of unknown function 429 (DUF429), and RSD, RelA_SpoT nucleotidyl transferase domain, the SYNTH domain responsible for (p)ppGpp synthesis activity]. MS_RHII-RSD is expressed and is constitutively active in vivo and behaves like a monofunctional (p)ppGpp synthetase in vitro. The occurrence of the RNase HII and (p)ppGpp synthetase domains together on the same polypeptide chain is suggestive of an in vivo role for this novel protein as a link connecting the essential life processes of DNA replication, repair, and transcription to the highly conserved stress survival pathway, the stringent response.
Authors:
Maya S Murdeshwar; Dipankar Chatterji
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-05-25
Journal Detail:
Title:  Journal of bacteriology     Volume:  194     ISSN:  1098-5530     ISO Abbreviation:  J. Bacteriol.     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-07-20     Completed Date:  2012-10-02     Revised Date:  2013-06-24    
Medline Journal Info:
Nlm Unique ID:  2985120R     Medline TA:  J Bacteriol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4003-14     Citation Subset:  IM    
Affiliation:
Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
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MeSH Terms
Descriptor/Qualifier:
DNA / metabolism
Gene Knockout Techniques
Guanosine Pentaphosphate / metabolism
Guanosine Tetraphosphate / metabolism
Hydrolysis
Ligases / genetics*,  metabolism*
Mycobacterium smegmatis / enzymology*,  genetics*
RNA / metabolism
Ribonuclease H / genetics*,  metabolism*
Chemical
Reg. No./Substance:
33503-72-9/Guanosine Tetraphosphate; 38918-96-6/Guanosine Pentaphosphate; 63231-63-0/RNA; 9007-49-2/DNA; EC 3.1.26.-/ribonuclease HII; EC 3.1.26.4/Ribonuclease H; EC 6.-/Ligases; EC 6.-/guanosine 3',5'-polyphosphate synthetases
Comments/Corrections

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