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The heat shock cognate protein from Dictyostelium affects actin polymerization through interaction with the actin‐binding protein cap32/34.
Author(s) -
Haus U.,
Trommler P.,
Fisher P.R.,
Hartmann H.,
Lottspeich F.,
Noegel A.A.,
Schleicher M.
Publication year - 1993
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1993.tb06054.x
Subject(s) - biology , actin binding protein , actin , dictyostelium , heat shock protein , microbiology and biotechnology , polymerization , dna binding protein , biophysics , cytoskeleton , biochemistry , actin cytoskeleton , transcription factor , polymer , materials science , gene , cell , composite material
During isolation of the F‐actin capping protein cap32/34 from Dictyostelium discoideum, a 70 kDa protein was copurified which by cloning and sequencing was identified as a heat shock cognate protein (hsc70). This protein exhibited a specific and MgATP‐dependent interaction with the heterodimeric capping protein. To investigate the protein‐protein interaction in vitro, we expressed all three polypeptides separately in Escherichia coli and performed reconstitution experiments of complete or truncated hsc70 with the 32 and 34 kDa subunits of the capping protein. Viscosity measurements and studies on the polymerization kinetics of pyrene‐labeled actin showed that hsc70 increased the capping activity of cap32/34 up to 10‐fold, whereas hsc70 alone had no effect on actin polymerization. In addition, hsc70 acted as a molecular chaperone by stimulating the refolding of the denatured 32 and 34 kDa subunits of the capping protein. To study the interaction of the two domains of hsc70 with cap32/34, the N‐terminal 42 kDa ATPase region and the C‐terminal 30 kDa tail of hsc70 were expressed separately in E. coli. The 32 and 34 kDa subunits were capable of associating with both domains of hsc70. The ATPase domain of hsc70, which is structurally related to actin, proved to be responsible for the increased capping activity of cap32/34, whereas the C‐terminal tail of hsc70 was involved in folding of the subunits of cap32/34. Our data indicate a novel linkage between 70 kDa heat shock proteins and the actin cytoskeleton.(ABSTRACT TRUNCATED AT 250 WORDS)