title: Phosphorylation by cyclic AMP-dependent protein kinase inhibits chaperone-like activity of human HSP22 in vitro.
abstract: Human small heat shock protein with molecular mass 22 kD (HSP22, HspB8) contains two Ser residues (Ser24 and Ser57) in consensus sequence RXS and is effectively phosphorylated by cAMP-dependent protein kinase in vitro. Mutation S24D did not affect, whereas mutations S57D or S24,57D prevented phosphorylation of HSP22 by cAMP-dependent protein kinase thus indicating that Ser57 is the primary site of phosphorylation. Phosphorylation (or mutation) of Ser57 (or Ser24 and Ser57) resulted in changes of the local environment of tryptophan residues and increased HSP22 susceptibility to chymotrypsinolysis. Mutations mimicking phosphorylation decreased dissociation of HSP22 oligomer at low concentration without affecting its quaternary structure at high protein concentration. Mutations S24D, S57D, and especially S24,57D were accompanied by decrease of chaperone-like activity of HSP22 if insulin and rhodanase were used as substrates. Thus, phosphorylation by cAMP-dependent protein kinase affects the structure and decreases chaperone-like activity of HSP22 in vitro.
authors.affiliation: Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.
authors.forename: A A
authors.initials: AA
authors.lastname: Shemetov
authors.forename: A S
authors.initials: AS
authors.lastname: Seit-Nebi
authors.forename: O V
authors.initials: OV
authors.lastname: Bukach
authors.forename: N B
authors.initials: NB
authors.lastname: Gusev
mesh_terms: D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D020836:Protein Structure, Quaternary
chemical_list: C413214:HSPB8 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases