Document Detail

Molecular characterization of ltp3 and ltp4, essential for C24-branched chain sterol side chain degradation in Rhodococcus rhodochrous DSM43269.
MedLine Citation:
PMID:  23059973     Owner:  NLM     Status:  Publisher    
A previously identified sterol catabolic gene cluster is widely dispersed among actinobacteria, enabling them to degrade and grow on naturally occurring sterols. We investigated the physiological roles of various genes by targeted inactivation in mutant RG32 of Rhodococcus rhodochrous, which selectively degrades sterol side chains. The ltp3 and ltp4 deletion mutants were each completely blocked in side chain degradation of β-sitosterol and campesterol, but not of cholesterol. These results indicated a role of ltp3 and ltp4 in the removal of C24 branches specifically. Bioinformatic analysis of the encoded Ltp3 and Ltp4 proteins revealed relatively high similarity to thiolase enzymes, typically involved in β-oxidation, but the catalytic residues characteristic for thiolase enzymes are not conserved in their amino acid sequences. Removal of the C24-branched side chain carbons of β-sitosterol was previously shown to proceed via aldolytic cleavage rather than by β-oxidation. Our results therefore suggest that ltp3 and ltp4 likely encode aldol-lyases, rather than thiolases. This is the first report on the molecular characterization of genes with specific and essential roles in carbon-carbon bond cleavage of C24-branched chain sterols in Rhodococcus strains, most likely acting as aldol-lyases. The results provide a clear contribution to our understanding of sterol degradation in actinobacteria.
Maarten Hotse Wilbrink; Robert van der Geize; Lubbert Dijkhuizen
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-11
Journal Detail:
Title:  Microbiology (Reading, England)     Volume:  -     ISSN:  1465-2080     ISO Abbreviation:  Microbiology (Reading, Engl.)     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9430468     Medline TA:  Microbiology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
University of Groningen.
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