1a2x

COMPLEX OF TROPONIN C WITH A 47 RESIDUE (1-47) FRAGMENT OF TROPONIN I

spinqualitylabelsall models 1a2x, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1a2x is a 2 chain structure with sequence from European rabbit. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CA Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [TNNC2_RABIT] 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. [TNNI2_RABIT] Troponin I is the inhibitory subunit of troponin, the thin filament regulatory complex which confers calcium-sensitivity to striated muscle actomyosin ATPase activity. 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 PubMed Troponin (Tn), the complex of three subunits (TnC, TnI, and TnT), plays a key role in Ca2+-dependent regulation of muscle contraction. To elucidate the interactions between the Tn subunits and the conformation of TnC in the Tn complex, we have determined the crystal structure of TnC (two Ca2+ bound state) in complex with the N-terminal fragment of TnI (TnI1-47). The structure was solved by the single isomorphous replacement method in combination with multiple wavelength anomalous dispersion data. The refinement converged to a crystallographic R factor of 22.2% (Rfree = 32.6%). The central, connecting alpha-helix observed in the structure of uncomplexed TnC (TnCfree) is unwound at the center (residues Ala-87, Lys-88, Gly-89, Lys-90, and Ser-91) and bent by 90 degrees. As a result, TnC in the complex has a compact globular shape with direct interactions between the N- and C-terminal lobes, in contrast to the elongated dumb-bell shaped molecule of uncomplexed TnC. The 31-residue long TnI1-47 alpha-helix stretches on the surface of TnC and stabilizes its compact conformation by multiple contacts with both TnC lobes. The amphiphilic C-end of the TnI1-47 alpha-helix is bound in the hydrophobic pocket of the TnC C-lobe through 38 van der Waals interactions. The results indicate the major difference between Ca2+ receptors integrated with the other proteins (TnC in Tn) and isolated in the cytosol (calmodulin). The TnC/TnI1-47 structure implies a mechanism of how Tn regulates the muscle contraction and suggests a unique alpha-helical regulatory TnI segment, which binds to the N-lobe of TnC in its Ca2+ bound conformation. Crystal structure of troponin C in complex with troponin I fragment at 2.3-A resolution.,Vassylyev DG, Takeda S, Wakatsuki S, Maeda K, Maeda Y Proc Natl Acad Sci U S A. 1998 Apr 28;95(9):4847-52. PMID:9560191 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Role of Troponin C in decreased muscle sensitivity to calcium Troponin

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