Genes involved in meso-diaminopimelate synthesis in Bacillus subtilis: identification of the gene encoding aspartokinase I
| Autor: | Dimitri Karamata, Cyrille Brandt, Claude-Alain H. Roten |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Genetics
Genetic Linkage Structural gene Mutant Temperature Locus (genetics) Peptidoglycan Bacillus subtilis Biology Diaminopimelic Acid biology.organism_classification Microbiology Isozyme Kinetics Solubility Biochemistry Genes Bacterial Putative gene Mutation Aspartate kinase Aspartate Kinase Transformation Bacterial Gene |
| Zdroj: | Journal of General Microbiology. 137:951-962 |
| ISSN: | 0022-1287 |
| Popis: | Summary: Thermosensitive mutants of Bacillus subtilis deficient in peptidoglycan synthesis were screened for mutations in the meso-diaminopimelate (ld-A2pm) metabolic pathway. Mutations in two out of five relevant linkage groups, IssB and IssD, were shown to induce, at the restrictive temperature, a deficiency in ld-A2pm synthesis and accumulation of UDP-MurNAc-dipeptide. Group IssB is heterogeneous; it encompasses mutations that confer deficiency in the deacylation of N-acetyl-ll-A2pm and accumulation of this precursor. Accordingly, these mutations are assigned to the previously identified locus dapE. Mutations in linkage group IssD entail a thermosensitive aspartokinase I. Therefore, they are most likely to affect the structural gene of this enzyme, which we propose to designate dapG. Mutation pyc-1476, previously reported to affect the pyruvate carboxylase, was shown to confer a deficiency in aspartokinase I, not in the carboxylase, and to belong to the dapG locus. dapG is closely linked to spoVF, the putative gene of dipicolinate synthase. In conclusion, mutations affecting only two out of eight steps known to be involved in ld-A2pm synthesis were uncovered in a large collection of thermosensitive mutants obtained by indirect selection. We propose that this surprisingly restricted distribution of the thermosensitive dap mutations isolated so far is due to the existence, in each step of the pathway, of isoenzymes encoded by separate genes. The biological role of different aspartokinases was investigated with mutants deficient in dapE and dapG genes. Growth characteristics of these mutants in the presence of various combinations of aspartate family amino acids allow a reassessment of a metabolic channel hypothesis, i.e. the proposed existence of multienzyme complexes, each specific for a given end product. |
| Databáze: | OpenAIRE |
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