title: Structural and functional characterization of calponin fragments.
abstract: Calponin from chicken gizzard consists of two principal components, possibly isoforms, separable by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing. Cleavage with 2-nitro-5-thiocyanobenzoic acid indicated that calponin contains 2 cysteine residues. Purified fragments of 30 and 21 kDa retained the following properties of the intact protein: actin-, tropomyosin- and calmodulin-binding, and ability to inhibit the actin-activated MgATPase activity of smooth muscle myosin. Both fragments, like intact calponin, were phosphorylated by protein kinase C which inhibited their binding to actin and relieved their inhibition of the ATPase. Tryptic digestion of calponin phosphorylated by protein kinase C generated 3 phosphopeptides with the following N-terminal sequences: FASQQGMTAYGTR, GASQQGMTVYGLP, and NHSGHVQ, each possessing a single phosphoserine.
authors: Department of Medical Biochemistry, University of Calgary, Alberta, Canada.
authors: S J
authors: SJ
authors: Winder
authors: M P
authors: MP
authors: Walsh
mesh_terms: D000199:Actins / Q000378:metabolism / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D002147:Calmodulin / Q000378:metabolism; D002645:Chickens; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D005895:Gizzard, Avian / Q000737:chemistry; D019791:Guanidine; D006146:Guanidines; D007525:Isoelectric Focusing; D008840:Microfilament Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009130:Muscle, Smooth / Q000201:enzymology; D009218:Myosins / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000502:physiology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D013861:Thiocyanates; D014335:Tropomyosin / Q000378:metabolism; D000096985:Calponins
chemical_list: D000199:Actins; D017301:Ca(2+) Mg(2+)-ATPase; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D019791:Guanidine; D006146:Guanidines; D008840:Microfilament Proteins; D009218:Myosins; D010446:Peptide Fragments; D011493:Protein Kinase C; D013861:Thiocyanates; D014335:Tropomyosin; D000096985:Calponins; C008658:2-nitro-5-thiocyanobenzoic acid