The actin-myosin subfragment-1 complex stabilized by phenyldiglyoxal

Abstract Nuclear magnetic resonance studies have revealed the importance of arginine residues in the actin-myosin interface (Moir, A. J. G., and Levine, B. A. (1986) J. Inorg. Chem. 27, 271-278). In the present study, we tested the involvement of these residues in the rigor complex between actin and subfragment-1 (S1) by chemical cross-linking experiments using phenyldiglyoxal. Two kinds of linkages were observed, one within the S1 heavy chain itself (120-kDa product) and the other between actin and the S1 heavy chain (200-kDa product). The phenyldiglyoxal had an effect similar to that of phenylglyoxal on S1 ATPase activities. We also show that phenyldiglyoxal (of 0.6-0.8 nm arm length) cross-links an arginine residue of the 50-kDa domain to one in the 20-kDa domain of the S1 heavy chain in the absence of actin or to an arginine in actin when actin is present. The presence of Mg2+, adenosine 5'-diphosphate or 5'-adenylyl imidodiphosphate suppressed the intermolecular linkage with actin, and favored the intramolecular cross-link, (i.e. between 50-kDa and 20-kDa fragments). We propose that the same arginyl residue in the N-terminal part of the 50-kDa domain can be cross-linked to a nearby arginine in either the 20-kDa domain or the actin molecule. In accordance with the amino acid sequence of each protein this also implies that the actin-myosin interaction involves arginine residues located either after residue 28 of the N-terminal part of actin, since this actin region is devoid of arginine residues, or in the N-terminal portion of the 50-kDa domain, i.e. between residues 239 and 455.