Localization of calponin binding sites in the structure of 90 kDa heat shock protein (Hsp90)

The structure of rabbit liver Hsp90 was reevaluated by limited trypsinolysis, N-terminal sequencing and determination of the site that is phosphorylated by casein kinase 11. Limited proteolysis results in formation of four groups of large peptides with M-r, in the range of 26-41 kDa, Peptides with M-r, 39-41 kDa were represented by large N-terminal and central peptides starting at residue 283 of the alpha-isoform of Hsp90. All sites phosphorylated by casein kinase 11 mere located in the large 39-41 kDa peptides, Peptides with M-r, 26-27 kDa were represented by short N-terminal and central peptides starting at Glu-400 of the alpha-isoform of Hsp90, The data of affinity chromatography and light scattering indicate that smooth muscle calponin interacts with Hsp90, The calponin binding sites are located in the large (37-41 kDa) N-terminal and in a short (26-27 kDa)central peptide starting at Glu-400 of the alpha-isoform of Hsp90, Phosphorylation by casein kinase 11 up to 2 mol of phosphate per mol of Hsp90 does not affect interaction of Hsp90 with calponin, (C) 1999 Federation of European Biochemical Societies.