Role of the C-terminal extremities of the smooth muscle myosin heavy chains: implication for assembly properties

The two light meromyosin isoforms from rabbit smooth muscle were prepared a s recombinant proteins in Escherichia coli, These species which differed on ly by their C-terminal extremity showed the same circular dichroism spectra and endotherms in measurements of differential scanning calorimetry. Their solubility properties were different at pH 7.0 in the absence of monovalen t salts. Their paracrystals formed at low pH differed by their aspect and n umber. These data suggest a role for the C-terminal extremity of myosin hea vy chains in the assembly of myosin molecules in filaments and consequently in the contractility of smooth muscles, (C) 1999 Federation of European Bi ochemical Societies.