Characterization of High-Molecular-Mass Heat Shock Proteins and 42°C-Specific Heat Shock Proteins of Murine Cells

Abstract

There are two isoforms of high-molecular-mass heat shock protein (HMM-HSP), hsp105A and hsp105B, in murine FM3A cells. To characterize the HMM-HSPs, we here purified hsp105A and hsp105B, as well as 42°C-specific HSPs that are specifically induced by continuous heating at 42°C, from the cytoplasmic extracts of the FM3A cells heat-shocked at 42°C for 8 h. Digestion of the hsp105A, hsp105B, and 42°C-specific HSPs with lysyl endopeptidase generated 17,000-Da polypeptide fragments in common, and the N-terminal amino acid sequences of the fragments revealed a homology with those of the adenosine binding domain of hsp70 family proteins and actin. Thus, the two isoforms of hsp105 and the 42°C-specific HSPs seemed to be very similar proteins having a ATP binding domain in common, and these HSPs may constitute a HMM-HSP family in murine cells.