This entry represents the alpha helical (AH) and Ribosome-InterSubunit (RIS) domains found in RelA/SpoT proteins, adjacent to the ACT domain [1,2]. AH domain interacts with A/R tRNA and links the very C-terminal subdomains with TGS domain. The RIS domain is part of the binding interface between the C-terminal region and the ribosome, bridging the large and the small ribosomal subunits. RIS contains a four-stranded beta-sheet and a short alpha-helix. RelA/SpoT-homologue proteins (RHS) mediate the stringent response in bacteria which enables its metabolic adaptation under stress conditions. These enzymes synthesise the second messenger (p)ppGpp, 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 [1-3].

1: Ribosome*RelA structures reveal the mechanism of stringent response activation. Loveland AB, Bah E, Madireddy R, Zhang Y, Brilot AF, Grigorieff N, Korostelev AA; Elife. 2016; [Epub ahead of print] PMID:27434674

2: Structural Basis for Regulation of the Opposing (p)ppGpp Synthetase and Hydrolase within the Stringent Response Orchestrator Rel. Pausch P, Abdelshahid M, Steinchen W, Schafer H, Gratani FL, Freibert SA, Wolz C, Turgay K, Wilson DN, Bange G; Cell Rep. 2020;32:108157. PMID:32937119

3: ppGpp: a global regulator in Escherichia coli. Magnusson LU, Farewell A, Nystrom T; Trends Microbiol. 2005;13:236-242. PMID:15866041