LIS - Legume Information System
Information about legume traits for crop improvement
CicerMine
v5.1.0.3
Cicer data from the Legume Information System
v5.1.0.3
Cicer data from the Legume Information System
| Type | Family |
| Description | Proteolytic enzymes that exploit serine in their catalytic activity are ubiquitous, being found in viruses, bacteria and eukaryotes [ ]. They include a wide range of peptidase activity, including exopeptidase, endopeptidase, oligopeptidase and omega-peptidase activity. Many families of serine protease have been identified, these being grouped into clans on the basis of structural similarity and other functional evidence []. Structures are known for members of the clans and the structures indicate that some appear to be totally unrelated, suggesting different evolutionary origins for the serine peptidases [].Not withstanding their different evolutionary origins, there are similarities in the reaction mechanisms of several peptidases. Chymotrypsin, subtilisin and carboxypeptidase C have a catalytic triad of serine, aspartate and histidine in common: serine acts as a nucleophile, aspartate as an electrophile, and histidine as a base [ ]. The geometric orientations of the catalytic residues are similar between families, despite different protein folds []. The linear arrangements of the catalytic residues commonly reflect clan relationships. For example the catalytic triad in the chymotrypsin clan (PA) is ordered HDS, but is ordered DHS in the subtilisin clan (SB) and SDH in the carboxypeptidase clan (SC) [, ].This group of serine peptidases, which includes HetR, are associated with heterocystous cyanobacteria and belong to MEROPS peptidase family S48 (clan S-). HetR is a DNA-binding serine-type protease required for heterocyst differentiation in heterocystous cyanobacteria under conditions of nitrogen deprivation. Mutation of HetR from of Anabaena sp. (strain PCC 7120) by site-specific mutagenesis of Ser-152 showed that this residue was one of the peptidase active site residues. It was suggested that peptidase activity might be needed for repression of HetR overproduction under conditions of nitrogen deprivation [ ]. Modification of Cys-48 prevented disulphide-bond formation and homodimerisation of HetR and DNA-binding. The homodimer of HetR binds the promoter regions of hetR, hepA, and patS, suggesting a direct control of the expression of these genes by HetR. The pentapeptide RGSGR, which is present at the C terminus of PatS, blocks heterocyst formation, inhibits the DNA binding of HetR and prevents hetR up-regulation [ ]. |
| Short Name | Pept_S48_HetR |
