1yv0
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(New page: 200px<br /><applet load="1yv0" size="450" color="white" frame="true" align="right" spinBox="true" caption="1yv0, resolution 7.0Å" /> '''Crystal structure of ...)
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Revision as of 04:56, 21 November 2007
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Crystal structure of skeletal muscle troponin in the Ca2+-free state
Overview
Troponin senses Ca2+ to regulate contraction in striated muscle., Structures of skeletal muscle troponin composed of TnC (the sensor), TnI, (the regulator), and TnT (the link to the muscle thin filament) have been, determined. The structure of troponin in the Ca(2+)-activated state, features a nearly twofold symmetrical assembly of TnI and TnT subunits, penetrated asymmetrically by the dumbbell-shaped TnC subunit. Ca ions are, thought to regulate contraction by controlling the presentation to and, withdrawal of the TnI inhibitory segment from the thin filament. Here, we, show that the rigid central helix of the sensor binds the inhibitory, segment of TnI in the Ca(2+)-activated state. Comparison of crystal, structures of troponin in the Ca(2+)-activated state at 3.0 angstroms, resolution and in the Ca(2+)-free state at 7.0 angstroms resolution shows, that the long framework helices of TnI and TnT, presumed to be a, Ca(2+)-independent structural domain of troponin are unchanged. Loss of Ca, ions causes the rigid central helix of the sensor to collapse and to, release the inhibitory segment of TnI. The inhibitory segment of TnI, changes conformation from an extended loop in the presence of Ca2+ to a, short alpha-helix in its absence. We also show that Anapoe, a detergent, molecule, increases the contractile force of muscle fibers and binds, specifically, together with the TnI switch helix, in a hydrophobic pocket, of TnC upon activation by Ca ions.
About this Structure
1YV0 is a Protein complex structure of sequences from Gallus gallus with MG as ligand. Full crystallographic information is available from OCA.
Reference
Ca(2+)-regulated structural changes in troponin., Vinogradova MV, Stone DB, Malanina GG, Karatzaferi C, Cooke R, Mendelson RA, Fletterick RJ, Proc Natl Acad Sci U S A. 2005 Apr 5;102(14):5038-43. Epub 2005 Mar 22. PMID:15784741
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