INTERACTION OF A CONSERVED PEPTIDE DOMAIN IN RECOMBINANT HUMAN VENTRICULAR MYOSIN LIGHT CHAIN-2 WITH MYOSIN HEAVY-CHAIN

Recent work on molecular genetics of mammalian contractile proteins ha s provided valuable insights into the basis of the heterogeneity of mu scle proteins and their regulated expression during development, yet i nformation on the precise role(s) of light chains in actomyosin intera ction and muscle function is still lacking. The selective increase in ventricular myosin light chain-2 (MLC2) in hypertrophied heart muscle has been implicated as a compensatory feature of myosin, but its relev ance to myosin function is not known. To investigate the role of cardi ac MLC2, we have isolated a full-length cDNA clone for human ventricul ar MLC2 and produced a full-length and N-terminal deleted MLC2 polypep tides in Escherichia coli using the bacterial expression vector pT7-7 system. The interaction of recombinant MLC2 with myosin heavy chain (M HC) and its subfragment-1 was studied using the full-length and trunca ted recombinant polypeptides. The results demonstrated that the bacter ially produced full-length human cardiac MLC2 exchanges effectively wi th the native MLC2 and binds with specificity to MHC and to intact myo fibrils. Domain mapping by deletion and in vitro exchange/competition analysis with a synthetic peptide suggests that a conserved central do main in MLC2 participates in the functional association of the two myo sin subunits.