4tnc
From Proteopedia
(New page: 200px<br /><applet load="4tnc" size="450" color="white" frame="true" align="right" spinBox="true" caption="4tnc, resolution 2.0Å" /> '''REFINED STRUCTURE OF ...) |
|||
| Line 1: | Line 1: | ||
| - | [[Image:4tnc.jpg|left|200px]]<br /><applet load="4tnc" size=" | + | [[Image:4tnc.jpg|left|200px]]<br /><applet load="4tnc" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="4tnc, resolution 2.0Å" /> | caption="4tnc, resolution 2.0Å" /> | ||
'''REFINED STRUCTURE OF CHICKEN SKELETAL MUSCLE TROPONIN C IN THE TWO-CALCIUM STATE AT 2-ANGSTROMS RESOLUTION'''<br /> | '''REFINED STRUCTURE OF CHICKEN SKELETAL MUSCLE TROPONIN C IN THE TWO-CALCIUM STATE AT 2-ANGSTROMS RESOLUTION'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The structure of troponin C has been refined at 2A resolution to an R | + | The structure of troponin C has been refined at 2A resolution to an R value of 0.172 using a total of 8,100 reflections. Troponin C has an unusual dumbbell shape with only the two C-domain high affinity sites III and IV occupied with metals, while the pair of N-domain low affinity sites I and II are devoid of metals. The coordination of the Ca2+ approaches seven with the last glutamic acid residue in each site forming an asymmetric bidentate ligand. The flanking helices in the metal-bound EF hands are in similar orientation (both 113 degrees) while in the apo sites they are more obtuse (134 and 149 degrees). The EF hands of holo sites III and IV are similar while the apo sites I and II are less similar (rms for backbone atoms, 0.78 and 1.44). The half-loops of the 12-residue holo and apo sites show better agreement than the full loops themselves, suggesting a hinge motion at the midpoint of the loops. The long central helix is stabilized by electrostatic interactions and salt bridges between charged side chains spaced at 3 or 4 residues along the helix. A cluster of water molecules encircle the long helix and hydrogen bond to the backbone carbonyls. At the beginning of the B-helix, a water molecule is interposed at each of two consecutive backbone NH...OC hydrogen bonds. The terminal pair of helices A/D (apo) match with E/H (holo), and the internal pair of helices B/C (apo) match with F/G (holo). Thus, muscle contraction may be triggered by Ca2+ binding to loops I and II which results in a concerted rearrangement of residues in the loops, including the essential Gly at position 6 in each loop. This rearrangement than causes a reorientation of helices B and C along with the BC linker. |
==About this Structure== | ==About this Structure== | ||
| - | 4TNC is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus] with CA as [http://en.wikipedia.org/wiki/ligand ligand]. This structure | + | 4TNC is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus] with <scene name='pdbligand=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure supersedes the now removed PDB entry 3TNC. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4TNC OCA]. |
==Reference== | ==Reference== | ||
| Line 17: | Line 17: | ||
[[Category: contractile system protein]] | [[Category: contractile system protein]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 19:14:32 2008'' |
Revision as of 17:14, 21 February 2008
|
REFINED STRUCTURE OF CHICKEN SKELETAL MUSCLE TROPONIN C IN THE TWO-CALCIUM STATE AT 2-ANGSTROMS RESOLUTION
Overview
The structure of troponin C has been refined at 2A resolution to an R value of 0.172 using a total of 8,100 reflections. Troponin C has an unusual dumbbell shape with only the two C-domain high affinity sites III and IV occupied with metals, while the pair of N-domain low affinity sites I and II are devoid of metals. The coordination of the Ca2+ approaches seven with the last glutamic acid residue in each site forming an asymmetric bidentate ligand. The flanking helices in the metal-bound EF hands are in similar orientation (both 113 degrees) while in the apo sites they are more obtuse (134 and 149 degrees). The EF hands of holo sites III and IV are similar while the apo sites I and II are less similar (rms for backbone atoms, 0.78 and 1.44). The half-loops of the 12-residue holo and apo sites show better agreement than the full loops themselves, suggesting a hinge motion at the midpoint of the loops. The long central helix is stabilized by electrostatic interactions and salt bridges between charged side chains spaced at 3 or 4 residues along the helix. A cluster of water molecules encircle the long helix and hydrogen bond to the backbone carbonyls. At the beginning of the B-helix, a water molecule is interposed at each of two consecutive backbone NH...OC hydrogen bonds. The terminal pair of helices A/D (apo) match with E/H (holo), and the internal pair of helices B/C (apo) match with F/G (holo). Thus, muscle contraction may be triggered by Ca2+ binding to loops I and II which results in a concerted rearrangement of residues in the loops, including the essential Gly at position 6 in each loop. This rearrangement than causes a reorientation of helices B and C along with the BC linker.
About this Structure
4TNC is a Single protein structure of sequence from Gallus gallus with as ligand. This structure supersedes the now removed PDB entry 3TNC. Full crystallographic information is available from OCA.
Reference
Refined structure of chicken skeletal muscle troponin C in the two-calcium state at 2-A resolution., Satyshur KA, Rao ST, Pyzalska D, Drendel W, Greaser M, Sundaralingam M, J Biol Chem. 1988 Feb 5;263(4):1628-47. PMID:3338985
Page seeded by OCA on Thu Feb 21 19:14:32 2008
