| Type: | Domain | Name: | ATP-dependent protease La (LON), substrate-binding domain |
| 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 signature defines the N-terminal domain of the archael, bacterial and eukaryotic lon proteases, which are ATP-dependent serine peptidases belonging to the MEROPS peptidase family S16 (lon protease family, clan SF). In the eukaryotes the majority of the proteins are located in the mitochondrial matrix [, ]. In yeast, Pim1, is located in the mitochondrial matrix, is required for mitochondrial function, is constitutively expressed but is increased after thermal stress, suggesting that Pim1 may play a role in the heat shock response [].This structure of this domain have been revealed [, , ]. | Short Name: | LON_substr-bd_dom |
