Deletion of the amino-terminal region of smooth or skeletal muscle myosin light chain kinase decreased Vmax without changing Km, and exchanging a 65-residue region rendered chimeric kinases inactive.
The amino-terminal region of the catalytic core in myosin light chain kinases is involved in light chain recognition, and calmodulin binding domains share structural elements necessary for regulation.
The molecular and biochemical properties of myosin light chain kinases from chicken skeletal and smooth muscle were investigated by recombinant DNA techniques. Deletion of the amino-terminal region of either the smooth or skeletal muscle myosin light chain kinase resulted in a decrease in Vmax with no significant change in Km values for light chain substrates. Skeletal/smooth muscle chimeric kinases were inactive when a 65-residue region amino-terminal of the catalytic core was exchanged between the two forms. Changing alanine 494 to glutamic acid within this region in the chicken skeletal muscle myosin light chain kinase increased the Km values for light chains 10-fold. These results are consistent with the hypothesis that the region amino-terminal of the catalytic core in myosin light chain kinases is involved in light chain recognition. A skeletal muscle kinase which contained the smooth muscle calmodulin binding domain remained regulated by Ca2+/calmodulin. Thus, the calmodulin binding domains of smooth and skeletal muscle myosin light chain kinases share structural elements necessary for regulation.
Leachman et al. (Sun,) reported a other. Recombinant DNA modifications of myosin light chain kinases vs. Wild-type kinases was evaluated on Biochemical properties (Vmax, Km) of chimeric kinases. Deletion of the amino-terminal region of smooth or skeletal muscle myosin light chain kinase decreased Vmax without changing Km, and exchanging a 65-residue region rendered chimeric kinases inactive.