title: Substrate specificity and inhibitor sensitivity of Ca2+/S100-dependent twitchin kinases.
abstract: Myosin-associated giant protein kinases of the titin/witchin-like superfamily have previously been implicated in the regulation of muscle function, based on genetic and physiological studies. We find that recombinant constitutively active Caenorhabditis elegans and Aplysia twitchin kinase fragments differ in their catalytic activities and peptide-substrate specificities, as well as in their sensitivities to the naphthalene sulfonamide inhibitors 1-(5-chloronaphthalenesulfonyl)-1H-hexahydro-1,4-diazepine (ML-7) and 1-(5-iodonaphthalenesulfonyl)-1H-hexahydro-1,4-diazepine (ML-9). The constitutively active Aplysia twitchin kinase fragment has a remarkably high activity (Vmax > 100 mumol.min-1.mg-1) towards some substrate peptides. The autoinhibited forms of these twitchin kinases can be activated in a Ca(2+)-dependent manner by the dimeric form of the S100A1 protein (S100A1(2)). The twitchin kinase S100A1(2)-binding site can also bind Ca2+/calmodulin but neither kinase is activated by calmodulin. The data provide a functional basis for the ongoing crystallographic study of twitchin kinase fragments.
authors.affiliation: St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia. j.heierhorst@medicine.unimelb.edu.au
authors.forename: J
authors.initials: J
authors.lastname: Heierhorst
authors.forename: X
authors.initials: X
authors.lastname: Tang
authors.forename: J
authors.initials: J
authors.lastname: Lei
authors.forename: W C
authors.initials: WC
authors.lastname: Probst
authors.forename: K R
authors.initials: KR
authors.lastname: Weiss
authors.forename: B E
authors.initials: BE
authors.lastname: Kemp
authors.forename: G M
authors.initials: GM
authors.lastname: Benian
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia / Q000201:enzymology; D017173:Caenorhabditis elegans / Q000201:enzymology; D029742:Caenorhabditis elegans Proteins; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D007700:Kinetics; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D009418:S100 Proteins / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D029742:Caenorhabditis elegans Proteins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D009124:Muscle Proteins; D010455:Peptides; D009418:S100 Proteins; C489233:unc-22 protein, C elegans; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009219:Myosin-Light-Chain Kinase; D002118:Calcium