How myosin motors work: new insights from coupling structural and functional insights

Molecular chaperones from Hsp90 and Hsp70 families are known to bind stably to the mutant p53 tumor suppressor protein, and transiently to the wild-type p53 in cells and in vitro [1, 2]. Using highly purified human recombinant proteins, we reconstituted the in vitro chaperone-dependent reactions of p53 binding to the WAF1 promoter-derived sequence. At the physiological temperature of 37°C, Hsp90 α or β molecular chaperones alone efficiently rescue the wt p53 promoter DNA binding activity from a thermal inactivation [3, 4]. At heat shock conditions of 40–42°C, the Hsp70 and Hsp40 chaperone machine is required to rescue wt p53. At these temperatures, Hsp90 stimulates the reaction by an indirect chaperoning, which requires a cooperation with Hsp70 and Hsp40 via Hop co-chaperone [4]. Thus, for the first time we were able to distinguish two different modes of the wt Hsp90 activity on a single substrate — direct and indirect. Moreover, the E42A Hsp90β Parnas Lecture