Mechanical and biochemical characterization of the contraction elicited by a calcium-independent myosin light chain kinase in chemically skinned smooth muscle.
The contraction induced by a Ca2+-independent myosin light chain kinase (MLCK-) was characterized in terms of isometric force (Fo), immediate elastic recoil (SE), unloaded shortening velocity (Vus), shortening under a constant load and ATPase activity of chemically skinned smooth muscle preparations. These parameters were compared to those measured in a Ca2+ -induced contraction to assess the nature of cross bridge interaction in the MLCK-induced contraction. Fo developed in chicken gizzard fibers as well as SE were similar in contractions elicited by either agent. Vus in the contraction induced by MLCK-(0.36 mg/ml) was similar though averaged 39.3 +/- 8.9% less than Vus induced by Ca2+ (1.6 X 10(-6) M) in the control fibers. Addition of Ca2+ (1.6 X 10(-6) M) to a contraction induced by MLCK-resulted in small increases in both Fo and Vus. Shortening under a constant load was similar for both types of contractions. The contraction induced by MLCK-was accompanied by an increased rate of ATP hydrolysis. The MLCK-induced contraction is thus kinetically similar though not identical to a contraction induced by Ca2+. We conclude that with respect to actin-myosin interaction, MLCK-and Ca2+ -induced contractions are similar.
Mrwa
U
U
Güth
K
K
Rüegg
J C
JC
Paul
R J
RJ
Boström
S
S
Barsotti
R
R
Hartshorne
D
D
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology; D002463:Cell Membrane Permeability; D002645:Chickens; D004548:Elasticity; D006168:Guinea Pigs; D007700:Kinetics; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology*; D009219:Myosin-Light-Chain Kinase; D011494:Protein Kinases / Q000502:physiology
D011494:Protein Kinases; D009219:Myosin-Light-Chain Kinase; D000251:Adenosine Triphosphatases; D002118:Calcium