The beta-isoform of heat shock protein hsp-90 is structurally related withhuman microtubule-interacting protein Mip-90

Through major research advances in the study of cytoskeletal organization, an integrated view of the complexity of this system has emerged. Recent fin dings on the microtubule-interacting protein Mip-90, which associates with microtubules and actin filaments in different cell domains, have shed light on its roles in cytoskeletal regulation. In order to study structural feat ures of Mip-90, we sequenced several peptide fragments. A comparative seque nce analysis revealed a high degree of similarity between the primary struc ture of this protein and the human heat shock protein of 90 kDa (hsp-90), T aken together, the present studies indicate the identity between Mip-90 and the the beta-isoform of hsp-90 (hsp-90 beta), Western blot assays with an anti-hsp-90 monoclonal antibody showed cross-reactivity of hsp90 and Mip-90 affinity purified from HeLa cells, Furthermore, the observed structural id entity of Mip-90 with the hsp-90 beta was sustained by immunoblot assays us ing monoclonal antibodies that specifically recognize the alpha- and beta-f orms of hsp-90,Comparative fingerprinting analysis,along with the evidence of a remarkably similar biochemical behavior of both hsp-90 and Mip-90 in d ifferent affinity chromatographic systems, supported these observations. Th ese studies, along with previous investigations, provide new data to elucid ate the functional significance of these interesting cellular components an d its relationships with other proteins linked to the cell architecture. (C ) 1999 Federation of European Biochemical Societies.