title: Change in the actin-myosin subfragment 1 interaction during actin polymerization.
abstract: To better characterize the conformational differences of G- and F-actin, we have compared the interaction between G- and F-actin with myosin subfragment 1 (S1) which had part of its F-actin binding site (residues 633-642) blocked by a complementary peptide or "antipeptide" (Chaussepied, P., and Morales, M. F. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 7471-7475). Light scattering, sedimentation, and electron microscopy measurements showed that, with the antipeptide covalently attached to the S1 heavy chain, S1 was not capable of inducing G-actin polymerization in the absence of salt. Moreover, the antipeptide-carrying S1 did not change the fluorescence polarization of 5-[2-(iodoacetyl)-aminoethyl]aminonaphthalene-1-sulfonic acid (1,5-IAEDANS)-labeled G-actin or of 1,5-IAEDANS-labeled actin dimer, compared to the control S1. This result, interpreted as a lack of interaction between G-actin and antipeptide-carrying S1, was confirmed further by the following experiments: in the presence of G-actin, antipeptide.S1 heavy chain was not protected against trypsin and papain proteolysis, and G-actin could not be cross-linked to antipeptide.S1 by 1-ethyl-3[-3-(dimethylamino)propyl]carbodiimide. In contrast, similar experiments showed that antipeptide.S1 was able to interact with nascent F-actin and with F-actin. Thus, blocking the stretch 633-642 of S1 heavy chain by the antipeptide strongly inhibits G-actin-S1 interaction but only slightly alters F-actin-S1 contact. We, therefore postulate that this stretch of skeletal S1 heavy chain is essential for G-actin-S1 interaction and that the G-F transformation generates new S1 binding site(s) on the actin molecule.
authors.affiliation: Cardiovascular Research Institute, University of California, San Francisco 94143-0524.
authors.forename: P
authors.initials: P
authors.lastname: Chaussepied
authors.forename: A A
authors.initials: AA
authors.lastname: Kasprzak
mesh_terms: D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000494:pharmacology; D007700:Kinetics; D008027:Light; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D009132:Muscles / Q000378:metabolism; D015879:Myosin Subfragments / Q000378:metabolism* / Q000648:ultrastructure; D011817:Rabbits; D012542:Scattering, Radiation; D014357:Trypsin
chemical_list: D000199:Actins; D046911:Macromolecular Substances; D015879:Myosin Subfragments; D014357:Trypsin; D005022:Ethyldimethylaminopropyl Carbodiimide