The DNase I binding loop (residues 38-52), the hydrophobic plug (residues 262-274), and the C ter... more The DNase I binding loop (residues 38-52), the hydrophobic plug (residues 262-274), and the C terminus region are among the structural elements of monomeric (G-) actin proposed to form the intermonomer interface in F-actin. To test the proximity and interactions of these elements and to provide constraints on models of F-actin structure, cysteine residues were introduced into yeast actin either at residue 41 or 265. These mutations allowed for speci®c cross-linking of F-actin between C41 and C265, C265 and C374, and C41 and C265 using dibromobimane and disul®de bond formation. The cross-linked products were visualized on SDS-PAGE and by electron microscopy. Model calculations carried out for the cross-linked F-actins revealed that considerable¯exibility or displacement of actin residues is required in the disul®de cross-linked segments to ®t these ®laments into model F-actin structures. The calculated, cross-linked structures showed a better ®t to the Holmes rather than the re®ned Lorenz model of F-actin. It is predicted on the basis of such calculations that image reconstruction of electron micrographs of disul®de cross-linked C41-C374 F-actin should provide a conclusive test of these two similar models of F-actin structure.
The DNase I binding loop (residues 38-52), the hydrophobic plug (residues 262-274), and the C ter... more The DNase I binding loop (residues 38-52), the hydrophobic plug (residues 262-274), and the C terminus region are among the structural elements of monomeric (G-) actin proposed to form the intermonomer interface in F-actin. To test the proximity and interactions of these elements and to provide constraints on models of F-actin structure, cysteine residues were introduced into yeast actin either at residue 41 or 265. These mutations allowed for speci®c cross-linking of F-actin between C41 and C265, C265 and C374, and C41 and C265 using dibromobimane and disul®de bond formation. The cross-linked products were visualized on SDS-PAGE and by electron microscopy. Model calculations carried out for the cross-linked F-actins revealed that considerable¯exibility or displacement of actin residues is required in the disul®de cross-linked segments to ®t these ®laments into model F-actin structures. The calculated, cross-linked structures showed a better ®t to the Holmes rather than the re®ned Lorenz model of F-actin. It is predicted on the basis of such calculations that image reconstruction of electron micrographs of disul®de cross-linked C41-C374 F-actin should provide a conclusive test of these two similar models of F-actin structure.
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Papers by Kaveh Kokabi