title: Brassica napus hsp90 can autophosphorylate and phosphorylate other protein substrates.
abstract: A Brassica napus cDNA encoding the 90 kDa heat shock protein, hsp90, was modified to add 6 histidines at the C-terminus and expressed in insect cells to prepare a recombinant histidine-tagged hsp90. The recombinant protein was purified over Ni2+-NTA agarose columns and its identity was confirmed by Western blotting, using a plant hsp90-specific antiserum. Incubation of purified hsp90 with [gamma-32P] ATP in the presence of Mn2+ resulted in its autophosphorylation on serine residues. The purified hsp90 could also phosphorylate other protein substrates such as histones and casein in the presence of Mn2+. Analysis of phosphorylated casein revealed that serine residues are phosphorylated by hsp90. This is the first demonstration that a cytosolic hsp90 homolog can phosphorylate other protein substrates.
authors.affiliation: Department of Microbiology and Immunology, The University of Western Ontario, London, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Park
authors.forename: C
authors.initials: C
authors.lastname: Yong Kang
authors.forename: P
authors.initials: P
authors.lastname: Krishna
mesh_terms: D000818:Animals; D001937:Brassica / Q000201:enzymology* / Q000378:metabolism; D002364:Caseins / Q000378:metabolism; D002417:Cattle; D018841:HSP90 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D019606:Phosphoamino Acids / Q000032:analysis; D010766:Phosphorylation; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D012694:Serine / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D002364:Caseins; D018841:HSP90 Heat-Shock Proteins; D006657:Histones; D019606:Phosphoamino Acids; D010940:Plant Proteins; D011994:Recombinant Proteins; D012710:Serum Albumin, Bovine; D012694:Serine; D006639:Histidine