title: Characterisation of the effects of mutation of the caldesmon sequence 691glu-trp-leu-thr-lys-thr696 to pro-gly-his-tyr-asn-asn on caldesmon-calmodulin interaction.
abstract: We have investigated the functional properties of a mutant (Cg1) derived from the C-terminal 99 amino acids of chicken caldesmon, 658-756 (658C) where the sequence 691glu-trp-leu-thr-lys-thr696 is changed to pro-gly-his-tyr-asn-asn. Cg1 bound Ca2+-calmodulin with (1/7)th of the affinity as compared to 658C or whole caldesmon. NMR titrations indicate that the contacts of Ca2+-calmodulin with the Trp-722 region of the peptide are retained but that those at the mutated site are lost. Most importantly Ca2+-calmodulin is not able to reverse the Cg1-induced inhibition. We conclude that the interaction of calmodulin with this caldesmon sequence is crucial for the reversal of caldesmon inhibition of actin-tropomyosin activation of myosin ATPase. The results are interpreted in terms of multisite attachment of actin and Ca2+-calmodulin to overlapping sequences in caldesmon domain 4b.
authors.affiliation: Imperial College School of Medicine at the National Heart and Lung Institute, Cardiac Medicine, London, UK.
authors.forename: P A
authors.initials: PA
authors.lastname: Huber
authors.forename: B A
authors.initials: BA
authors.lastname: Levine
authors.forename: O
authors.initials: O
authors.lastname: Copeland
authors.forename: S B
authors.initials: SB
authors.lastname: Marston
authors.forename: M
authors.initials: M
authors.lastname: El-Mezgueldi
mesh_terms: D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002645:Chickens; D004791:Enzyme Inhibitors / Q000378:metabolism*; D016296:Mutagenesis; D009218:Myosins / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011817:Rabbits; D012756:Sheep; D013329:Structure-Activity Relationship; D017186:Titrimetry
chemical_list: D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D004791:Enzyme Inhibitors; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins; D002118:Calcium