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ATPase-like domain of the ASKHA (Acetate and Sugar Kinases/Hsc70/Actin) superfamily The ASKHA superfamily, also known as actin-like ATPase domain superfamily, includes acetate and sugar kinases, heat-shock cognate 70 (Hsp70) and actin family proteins. They either function as conformational hydrolases (e.g. Hsp70, actin) that perform simple ATP hydrolysis, or as metabolite kinases (e.g. glycerol kinase) that catalyze the transfer of a phosphoryl group from ATP to their cognate substrates. Both activities depend on the presence of specific metal cations. ASKHA superfamily members share a common core fold that includes an actin-like ATPase domain consisting of two subdomains (denoted I & II) with highly similar ribonuclease (RNase) H-like folds. The fold of each subdomain is characterized by a central five strand beta-sheet and flanking alpha-helices. The two subdomains form an active site cleft in which ATP binds at the bottom. Another common feature of ASKHA superfamily members is the coupling of phosphoryl-group transfer to conformational rearrangement, leading to domain closure. Substrate binding triggers protein motion.
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