title: Caldesmon is a Ca2+-regulatory component of native smooth-muscle thin filaments.
abstract: Thin-filament preparations from four smooth muscle types (gizzard, stomach, trachea, aorta) all activate myosin MgATPase activity, are regulated by Ca2+, and contain actin, tropomyosin and a 120000-140000-Mr protein in the molar proportions 1:1/7:1/26. The 120000-140000-Mr protein from all sources is a potent inhibitor of actomyosin ATPase activity. Peptide-mapping and immunological evidence is presented showing that it is identical with caldesmon. Quantitative immunological data suggest that caldesmon is a component of all the thin filaments and that the thin-filament-bound caldesmon accounts for all the caldesmon in intact tissue. The myosin light-chain kinase content of thin-filament preparations was found to be negligible. We propose that caldesmon-based thin-filament Ca2+ regulation is a physiological mechanism in all smooth muscles.
authors.forename: S B
authors.initials: SB
authors.lastname: Marston
authors.forename: W
authors.initials: W
authors.lastname: Lehman
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D011232:Chemical Precipitation; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D066298:In Vitro Techniques; D009124:Muscle Proteins / Q000378:metabolism; D009130:Muscle, Smooth / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis
chemical_list: D002148:Calmodulin-Binding Proteins; D009124:Muscle Proteins; D010446:Peptide Fragments; D000251:Adenosine Triphosphatases; D002118:Calcium