DOMAIN-STRUCTURE OF A MAMMALIAN MYOSIN I-BETA

We have determined the primary structure of a myosin I (called mammali an myosin I beta, MMI beta) from bovine brain and identified its funct ional domains, The protein was previously purified from brain and adre nal gland. Several constructs were generated and expressed in Escherch ia coli as glutathione S-transferase fusion proteins and the recombina nt proteins were recognized by monoclonal antibodies that recognize ei ther ''head'' or ''tail'' domains of native myosin I. A gel overlay me thod was used to confirm that calmodulin binds to the consensus calmod ulin-binding sequence in MMI beta. Binding assays were used to detect interaction with anionic phospholipid vesicles. We conclude that MMI b eta consists of an amino-terminal 80.5-kDa domain that contains the AT P- and actin-binding sites, followed by an 8.5-kDa domain with three c almodulin-binding sequences and a basic 30-kDa carboxyl-terminal tail segment that binds to anionic phospholipids and membranes.