nucleotide-binding domain (NBD) of heat shock 70 kDa protein 13 (HSPA13) and similar proteins
HSPA13, also called 70-kDa heat shock protein 13, STCH, microsomal stress-70 protein ATPase core, or stress-70 protein chaperone microsome-associated 60 kDa protein, has peptide-independent ATPase activity. It belongs to the heat shock protein 70 (HSP70) family of chaperones that assist in protein folding and assembly and can direct incompetent "client" proteins towards degradation. Typically, HSP70s have a nucleotide-binding domain (NBD) and a substrate-binding domain (SBD). The nucleotide sits in a deep cleft formed between the two lobes of the NBD. The two subdomains of each lobe change conformation between ATP-bound, ADP-bound, and nucleotide-free states. ATP binding opens up the substrate-binding site; substrate-binding increases the rate of ATP hydrolysis. HSP70 chaperone activity is regulated by various co-chaperones: J-domain proteins and nucleotide exchange factors (NEFs). HSPA13 contains an NBD but lacks an SBD. It may function to regulate cell proliferation and survival and modulate the TRAIL-mediated cell death pathway. The HSPA13 gene is a candidate stomach cancer susceptibility gene; a mutation in the NBD coding region of HSPA13 has been identified in stomach cancer cells. The NBD of HSPA13 interacts with the ubiquitin-like proteins Chap1 and Chap2, implicating HSPA13 in regulating cell cycle and cell death events. HSPA13 is induced by the Ca2+ ionophore A23187.
Jiyao W et al.(2023). "The conserved domain database in 2023.",