title: The functional significance of the last 5 residues of the C-terminus of cardiac troponin I.
abstract: The C-terminal region of cardiac troponin I (cTnI) is known to be important in cardiac function, as removal of the last 17 C-terminal residues of human cTnI has been associated with myocardial stunning. To investigate the C-terminal region of cTnI, three C-terminal deletion mutations in human cTnI were generated: Δ1 (deletion of residue 210), Δ3 (deletion of residues 208-210), and Δ5 (deletion of residues 206-210). Mammalian two-hybrid studies showed that the interactions between cTnI mutants and cardiac troponin C (cTnC) or cardiac troponin T (cTnT) were impaired in Δ3 and Δ5 mutants when compared to wild-type cTnI. Troponin complexes containing 2-[4'-(iodoacetamido) anilino] naphthalene-6-sulfonic acid (IAANS) labeled cTnC showed that the troponin complex containing cTnI Δ5 had a small increase in Ca(2+) affinity (P < 0.05); while the cTnI Δ1- and Δ3 troponin complexes showed no difference in Ca(2+) affinity when compared to wild-type troponin. In vitro motility assays showed that all truncation mutants had increased Ca(2+) dependent motility relative to wild-type cTnI. These results suggest that the last 5 C-terminal residues of cTnI influence the binding of cTnI with cTnC and cTnT and affect the Ca(2+) dependence of filament sliding, and demonstrate the importance of this region of cTnI.
authors.affiliation: Department of Neurobiology, Physiology, and Behavior, University of California, Davis, 95616, USA.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Gilda
authors.affiliation: Department of Neurobiology, Physiology, and Behavior, University of California, Davis, 95616, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA.
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Martinez
authors.affiliation: Department of Neurobiology, Physiology, and Behavior, University of California, Davis, 95616, USA.
authors.forename: Susan T
authors.initials: ST
authors.lastname: Nguyen
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA.
authors.forename: P Bryant
authors.initials: PB
authors.lastname: Chase
authors.affiliation: Department of Neurobiology, Physiology, and Behavior, University of California, Davis, 95616, USA. Electronic address: avgomes@ucdavis.edu.
authors.forename: Aldrin V
authors.initials: AV
authors.lastname: Gomes
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry; D000251:Adenosine Triphosphatases / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D017353:Gene Deletion; D006321:Heart / Q000502:physiology; D006801:Humans; D008856:Microscopy, Fluorescence; D009154:Mutation; D017682:Myocardial Stunning; D009206:Myocardium / Q000378:metabolism*; D000072417:Protein Domains; D019209:Troponin C / Q000737:chemistry*; D019210:Troponin I / Q000737:chemistry*; D020798:Two-Hybrid System Techniques
chemical_list: D019209:Troponin C; D019210:Troponin I; D000251:Adenosine Triphosphatases; D002118:Calcium
keywords: Calcium; Heart; In vitro motility assay; Mammalian two-hybrid; Troponin I; Unloaded filament sliding