| Primary Identifier | IPR045600 | Type | Domain |
| Short Name | RelA/SpoT_AH_RIS |
| description | This entry represents the alpha helical (AH) and Ribosome-InterSubunit (RIS) domains found in RelA/SpoT proteins, adjacent to the ACT domain [, ]. AH interacts with A/R tRNA and connects the RIS domain with the TGS domain. RIS domain is part of the binding interface between the C-terminal region and the ribosome, bridging the largeand the small ribosomal subunits. RIS contains a four-stranded β-sheet and a short α-helix.RelA/SpoT-homologue proteins (RHS) mediate the stringent response in bacteria which enables its metabolic adaptation under stress conditions. These enzymes synthesize the second messenger (p)ppGpp, a small molecule also known as 'alarmone', which is a regulatory metabolite of the stringent response, characterised by growth arrest and the modulation of gene expression in response to various nutritional stresses [, , ]. Including in this group of proteins are RelA and SpoT, whose functions differ somewhat. RelA () produces pppGpp (or ppGpp) from ATP and GTP (or GDP), while SpoT () is a bifunctional enzyme that degrades ppGpp, but can also act as a ppGpp synthetase. In many species, a single homologue to SpoT and RelA , Rsh, appears responsible for both ppGpp synthesis and ppGpp degradation [, , ]. ppGpp together with c-di-GMP play an important role to control biofilm formation in response to translational stress [].These enzymes consist of a N-terminal domain which harbor (p)ppGpp hydrolase and synthetase activity and a stress-perceiving and regulatory C-terminal domain, which comprising four sub-domains: the TGS (ThrRS, GTPase, and SpoT), AH (alpha helical), RIS (ribosome inter-subunit), and ACT (aspartate kinase, chorismate mutase, TyrA) [, ]. |
