Motion in Citrate Synthase [cs]

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Classification Known Domain Motion, Shear Mechanism [D-s-2]

Structures 1CTS Conformation 1 [ PartsList ] 3CTS Conformation 2

Description Shear motions at many helix-helix interfaces shift mainchain atoms up to 10 A. Citrate synthase is one of the clearest examples of a domain closure occurring through shear motions. The molecule is a dimer, and each monomer comprises a large domain, containing 15 helices, and a small domain, containing 5 helices, with the active site cleft between them. The domain closure involves the small domain closing over the large one, burying the substrates in the active site. An extensive interface between the large and small domains prevents closure taking place through a hinge mechanism. Closure is produced by the summation of many small shear motions between pairs of packed helices. The overall motion results in a helix on the far side of the small domain shifting by 10 A and rotating by 28 degrees, thereby moving an adjacent loop over the active site. Each local shear motion involves one helix moving relative to another by main-chain rotations and shifts of up to 13 degrees and 1.8 A. To a good approximation, the main chain of each helix moves without deformation as a rigid body. The shear motions are facilitated by small deformations in the loops linking the helices.

Particular values describing motion Experimental Methods = x (Traditional x-ray) Creation Date = 19970822 Modification Date = 19970822

References A M Lesk and C Chothia (1984). Mechanisms of Domain Closure in Proteins. J. Mol. Biol. 174: 175-91. [Medline info for 94082290] S Remington, G Wiegand and R Huber (1982). Crystallographic refinement and atomic models of two different forms of citrate synthase at 2.7 and 1.7 Å resolution. J. Mol. Biol. 158: 111-152. [Medline info for 94082290]

Data and Graphics Graphic-2 Schematic showing helices in citrate synthase (from Lesk & Chothia, 1984). Graphic-3 Schematic (from Lesk & Chothia, 1984) showing local movement (rot. and trans.) of pairs of helices (left) and overall movement (right) of these same helices. Graphic-1 Overall motion.

GO terms associated with structures Molecular function transferase activity, transferring acyl groups, acyl groups converted into alkyl on transfer, citrate (Si)-synthase activity Cellular component cytoplasm Biological process main pathways of carbohydrate metabolism, tricarboxylic acid cycle

Morphs

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Best representative Morph Morph name Structure #1 Structure #2 Residues [ ] [ ]

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Copyright 1995-2005 M. Gerstein, W. Krebs, S. Flores, N. Echols, and others
Email: Mark.Gerstein _at_ yale.edu