Abstract
BackgroundPolyamine synthesis produces methylthioadenosine, which has to be disposed of. The cell recycles it into methionine through methylthioribose (MTR). Very little was known about MTR recycling for methionine salvage in Bacillus subtilis.ResultsUsing in silico genome analysis and transposon mutagenesis in B. subtilis we have experimentally uncovered the major steps of the dioxygen-dependent methionine salvage pathway, which, although similar to that found in Klebsiella pneumoniae, recruited for its implementation some entirely different proteins. The promoters of the genes have been identified by primer extension, and gene expression was analyzed by Northern blotting and lacZ reporter gene expression. Among the most remarkable discoveries in this pathway is the role of an analog of ribulose diphosphate carboxylase (Rubisco, the plant enzyme used in the Calvin cycle which recovers carbon dioxide from the atmosphere) as a major step in MTR recycling.ConclusionsA complete methionine salvage pathway exists in B. subtilis. This pathway is chemically similar to that in K. pneumoniae, but recruited different proteins to this purpose. In particular, a paralogue or Rubisco, MtnW, is used at one of the steps in the pathway. A major observation is that in the absence of MtnW, MTR becomes extremely toxic to the cell, opening an unexpected target for new antimicrobial drugs. In addition to methionine salvage, this pathway protects B. subtilis against dioxygen produced by its natural biotope, the surface of leaves (phylloplane).
Highlights
Polyamine synthesis produces methylthioadenosine, which has to be disposed of
We demonstrate here that proteins YkrUWXYZ are needed for MTR recycling into methionine in B. subtilis, while YkrV, an aminotransferase, is probably more specific of methionine transamination, but is dispensable in the present conditions because of the present of a variety of izozymes
Transposon insertion mutations and phenotype of inactivated mutants The MTR analog trifluormethylthioribose (3F-MTR) is toxic if the methyl sulfur moiety of the molecule is recycled [9]. This molecule was an excellent candidate to explore the steps needed for MTR recycling to methionine
Summary
Polyamine synthesis produces methylthioadenosine, which has to be disposed of. The cell recycles it into methionine through methylthioribose (MTR). Very little was known about MTR recycling for methionine salvage in Bacillus subtilis. In Escherichia coli this molecule is excreted in the medium [1] while in Klebsiella pneumoniae it constitutes the methionine salvage pathway, being metabolized back into methionine [2,3]. In eukaryotic parasites it is recycled into methionine, presumably through a pathway similar to that in K. pneumoniae[4]. Henkin and co-workers found that the corresponding coding sequence (CDS) was preceded (page number not for citation purposes)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
