TY - JOUR
T1 - Gizzard Ca2+-independent myosin light chain kinase
T2 - Evidence in favor of the phosphorylation theory
AU - Walsh, M. P.
AU - Bridenbaugh, R.
AU - Kerrick, W. G.L.
AU - Hartshorne, D. J.
PY - 1983/1/1
Y1 - 1983/1/1
N2 - Limited digestion of calmodulin (CaM)-dependent myosin light chain kinase from turkey gizzard with α-chymotrypsin in the presence of bound CaM generated an 80,000-dalton kinase fragment that was fully active in the absence of Ca2+. This kinase catalyzed specific Ca2+-independent phosphorylation of the 20,000-dalton light chain of myosin using isolated light chains, intact myosin, and actomyosin. Phosphorylation of myosin in the absence of Ca2+ allowed us to dissociate myosin phosphorylation from other potential Ca2+-dependent regulatory mechanisms, thus permitting an evaluation of the postulated central role of myosin phosphorylation in the regulation of smooth muscle contraction. Ca2+-independent myosin phosphorylation was found to cause loss of Ca2+ sensitivity of actin-activated myosin ATPase activity in a crude actomyosin preparation, and tension development in skinned smooth muscle fibers in the absence of Ca2+. Myosin phosphorylation is, therefore, the key event in actin activation of ATPase activity and initiation of contraction in skinned chicken gizzard fibers.
AB - Limited digestion of calmodulin (CaM)-dependent myosin light chain kinase from turkey gizzard with α-chymotrypsin in the presence of bound CaM generated an 80,000-dalton kinase fragment that was fully active in the absence of Ca2+. This kinase catalyzed specific Ca2+-independent phosphorylation of the 20,000-dalton light chain of myosin using isolated light chains, intact myosin, and actomyosin. Phosphorylation of myosin in the absence of Ca2+ allowed us to dissociate myosin phosphorylation from other potential Ca2+-dependent regulatory mechanisms, thus permitting an evaluation of the postulated central role of myosin phosphorylation in the regulation of smooth muscle contraction. Ca2+-independent myosin phosphorylation was found to cause loss of Ca2+ sensitivity of actin-activated myosin ATPase activity in a crude actomyosin preparation, and tension development in skinned smooth muscle fibers in the absence of Ca2+. Myosin phosphorylation is, therefore, the key event in actin activation of ATPase activity and initiation of contraction in skinned chicken gizzard fibers.
UR - http://www.scopus.com/inward/record.url?scp=0020646886&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0020646886&partnerID=8YFLogxK
M3 - Article
C2 - 6848377
AN - SCOPUS:0020646886
VL - 42
SP - 45
EP - 50
JO - Federation Proceedings
JF - Federation Proceedings
SN - 0014-9446
IS - 1
ER -