title: Contractile protein interactions in smooth muscle.
abstract: Smooth muscle tone and 'holding economy' depend on the rate constants governing the cross-bridge cycle. Thus, calcium activation via calmodulin-dependent myosin light chain phosphorylation may determine the apparent rate constant ('f') at which cross-bridges enter the force-generating state, forming actin-attached, strongly bound cross-bridges. This phosphorylation of the light chain may be inhibited in skinned fibers by a peptide mimic of the calmodulin recognition site of the myosin light chain kinase (RS 20) that relaxes smooth muscle. In smooth muscle, the apparent cross-bridge detachment rate constant ('g') also seems to be variable, a low constant allowing for a high holding economy and low shortening velocity in the 'latch state'. It may also account for force maintenance at low levels of myosin phosphorylation. Additionally, cross-bridge attachment may, however, be also controlled by other regulatory proteins such as calponin and caldesmon.
authors.affiliation: Department of Physiology II, University of Heidelberg, FRG.
authors.forename: J C
authors.initials: JC
authors.lastname: Rüegg
authors.forename: G
authors.initials: G
authors.lastname: Pfitzer
mesh_terms: D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D002645:Chickens; D003285:Contractile Proteins / Q000378:metabolism*; D005895:Gizzard, Avian / Q000378:metabolism; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010766:Phosphorylation
chemical_list: D000199:Actins; D002147:Calmodulin; D003285:Contractile Proteins; D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D009219:Myosin-Light-Chain Kinase; D000251:Adenosine Triphosphatases; D009218:Myosins; D002118:Calcium