The 70 kDa family of heat-shock proteins (hsp 70s and hsc 70s) can facilitate protein transport to several organelles. This process is thought to involve electrostatic interactions between hsp 70s and the cellular protein targeting sequences. Analysis of the highly conserved structural and functional properties of the hsp 70 family indicated that they may cross-link cellular proteins to the actin microfilament network. Direct experimental support for this hypothesis was provided by the finding that hsp 70 is constitutively bound to actin through hydrophobic interactions. The cross-linker model may provide an explanation for the mechanism by which the cytoskeletal matrix could mediate various cellular processes.
