Regulation of alpha-helical coiled-coil dimerization in chicken skeletal muscle light meromyosin

The dimerization specificity of the light meromyosin (LMM) domain of chicke n neonatal and adult myosin isoforms was analyzed by metal chelation chroma tography. Our results show that neonatal and adult LMMs associate preferent ially, although not exclusively, as homodimeric coiled-coils. Using chimeri c LMM constructs combining neonatal and adult sequences, we observed that a stretch of 183 amino acids of sequence identity at the N terminus of the L MM was sufficient to allow the adult LMM to dimerize in a non-selective man ner. In contrast, sequence identity in the remaining C-terminal 465 amino a cids had only a modest effect on the dimerization selectivity of the adult isoform. Sequence identity at the N terminus also promoted dimerization of the neonatal LMM to a greater degree than sequence identity at the C termin us. However, the N terminus had only a partial effect on the dimerization s pecificity of the neonatal sequence, and residues distributed throughout th e LMM were capable of affecting dimerization selectivity of this isoform. T hese results indicated that dimerization preference of the neonatal and adu lt isoforms was affected to a different extent by sequence identity at a gi ven region of the LMM.