2jt8 | pdb_00002jt8
Solution structure of the F153-to-5-flurotryptophan mutant of human cardiac troponin C
Structural highlights
Disease[TNNC1_HUMAN] Defects in TNNC1 are the cause of cardiomyopathy dilated type 1Z (CMD1Z) [MIM:611879]. Dilated cardiomyopathy is a disorder characterized by ventricular dilation and impaired systolic function, resulting in congestive heart failure and arrhythmia. Patients are at risk of premature death.[1] Defects in TNNC1 are the cause of familial hypertrophic cardiomyopathy type 13 (CMH13) [MIM:613243]. A hereditary heart disorder characterized by ventricular hypertrophy, which is usually asymmetric and often involves the interventricular septum. The symptoms include dyspnea, syncope, collapse, palpitations, and chest pain. They can be readily provoked by exercise. The disorder has inter- and intrafamilial variability ranging from benign to malignant forms with high risk of cardiac failure and sudden cardiac death.[2] [3] [4] [5] Function[TNNC1_HUMAN] Troponin is the central regulatory protein of striated muscle contraction. Tn consists of three components: Tn-I which is the inhibitor of actomyosin ATPase, Tn-T which contains the binding site for tropomyosin and Tn-C. The binding of calcium to Tn-C abolishes the inhibitory action of Tn on actin filaments. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed19F NMR spectroscopy is potentially a powerful tool for probing protein properties in situ. However, results obtained using this technique are relevant only if the 19F probe offers minimal perturbation to the surrounding environment. In this paper, we examine the effect of 5-fluorotryptophan (5fW) incorporation on the three-dimensional structure of cardiac troponin-C (cTnC), with the intention of developing a 19F-labeled TnC for use in in situ 19FNMR. We find that, in general, 5fW does not perturb the structure of the protein significantly. Replacement of residue Phe 153 with 5fW produces no noticeable change in protein conformation. However, replacement of residue Phe 104 with 5fW produces a folding behavior that is dependent on the Escherichia coli strain used to express the mutant. The orientations of the indole rings in these mutants are such that the Trp residue adopts a chi2 of approximately 90 degrees in the F104W mutant and approximately -100 degrees in the F153W mutant. Using results from 19F-1H heteronuclear NOE experiment, we show the replacement of L-Trp with 5fW at these positions does not change the orientation of the indole ring and the spread of the 5fW side-chain dihedral angles increases moderately for the F104(5fW) mutant and not at all for the F153(5fW) mutant. Based on these structures, we conclude that the substitution of Phe by 5fW at these two positions has minimal effects on the structure of cTnC and that the 5fW indole rings in both mutants have well defined orientation, making the two mutants viable candidates for use in in situ 19F NMR spectroscopy. Effects of Phe-to-Trp mutation and fluorotryptophan incorporation on the solution structure of cardiac troponin C, and analysis of its suitability as a potential probe for in situ NMR studies.,Wang X, Mercier P, Letourneau PJ, Sykes BD Protein Sci. 2005 Sep;14(9):2447-60. PMID:16131667[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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