Year-end Sale % OFF 
Abstract
Smooth muscle myosin light chain kinase was purified from turkey gizzards. The enzyme was extracted from washed myofibrils and the final step of purification was affinity chromatography using calmodulin coupled to Sepharose 4B. The purified enzyme was characterized with respect to its physical, chemical, and kinetic properties. It has a molecular weight of 130,000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis and 124,000 by sedimentation equilibrium centrifugation under nondenaturing conditions. It is an asymmetric molecule with a Stokes radius of 75 A, a sedimentation coefficient of 4.45 S, and a frictional coefficient of 1.85. Smooth muscle myosin light chain kinase is dependent on the calcium-binding protein calmodulin for activity. It has an apparent K0.5 for calmodulin of 10(-9) M and binds 1 mol of calmodulin/mol of myosin kinase in the presence of calcium. The binding of calmodulin increases the sedimentation coefficient from 4.45 S to 5.05 S, and the Stokes radius from 75 A to 79 A, and does not alter the frictional coefficient. The enzyme has a Km for ATP and the 20,000-dalton light chain of smooth muscle myosin of 50 microM and 5 microM, respectively. It phosphorylates the 20,000-dalton light chain of smooth muscle myosin more rapidly than the equivalent light chain from cardiac and skeletal muscles. It does not phosphorylate histones, alpha-casein, phosphorylase kinase, or phosphorylase b at a significant rate.
Highlights
Amino acid composition of chicken gizzard myosin kinase based on aM,of 105,000 [17]
Smooth musclemyosin kinase was isolated from turkey gizzards and purified 60-fold from washed myofibrils
Turkey gizzard muscle which corresponds to a concentration The isolated 20,000-dalton light chain of turkey gizzard of approximately 1.2 X lop6M
Summary
(Received for publication, January 6, 1981, and in revised form, March 27, 1981). From the Cardiology Branch, National HeartL, ung, and Blood Institute andthe Laboratory of Biochemistry, National Cancer Institute, National Institutesof Health, Bethesda, Maryland 20205. Smooth muscle myosin light chain kinase was puri- Ca2+for its activity [16]. The enzyme has a K,,, for ATP and the 20,000-dalton are presented on the physical, chemical,and kinetic properties light chain of smooth muscle myoosfin PM and 5p ~ ,of this enzyme in the presence and absence of bound calmodrespectively. Smooth musclemyosin light chain kinase catalyzes the transfer of the y-phosphate from ATPto smooth muscle myosin This reaction plays a major role in regulating smooth muscle contraction
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
