Isolation and characterization of three Dictyostelium myosin-I isozymes.

摘要: Using ion exchange chromatography and an ATP-dependent actin precipitation step, we have isolated three myosin-I isozymes that, together, account for most of the K+EDTA-ATPase activity recovered from extracts Dictyostelium. The two major isozymes, present in approximately equal amounts, had apparent molecular masses 125 kDa on SDS gels been identified by amino acid sequence analysis as products Dictyostelium myosin-IB (DMIB) myosin-ID (DMID) genes. DMIB, with a specific 10-fold higher than DMID, was responsible cell extracts. third isozyme, low mass 137 is too large to be product any known DMIB eluted DE53 cellulose columns distinct peaks (II III). Addition phosphatase inhibitor okadaic extraction buffer increased fraction growth phase cells peak III 35 70%. III, but not II, displayed significant level actin-activated MgATPase activity. These results indicate that represents phosphorylated, actin-activatable form DMIB.