Motion in Aspartate Transcarbamoylase (ATCase) [atcase]

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Classification Known Subunit Motion, Involving Allostery [S-a-2]

Structures
5AT1 Conformation 2 [ PartsList ]
8ATC Conformation 1 [ PartsList ]

Description
Quaternary structure motion: ATCase is composed of 6 regulatory subunits and 6 catalytic subunits. The 6 catalytic subunits are arranged as a sandwich (i.e. dimer) of 2 trimers, sharing the same (3-fold) symmetry axis. The 6 regulatory subunits are divided into three dimers, each of which runs between both sides of the catalytic trimer sandwich. In moving from the low to high affinity state (T to R), the regulatory dimers rotate by ~15 degrees about their dimer axes. Both parts of the catalytic trimer sandwich, in turn, separate by ~12 A along the 3-fold axis and rotate by ~10 degrees about this same axis. Tertiary structure motion: Each catalytic subunit is composed of two domains (aspartate and carbamoyl phosphate), and these domains close around the active site in the T to R transition, thus coupling tertiary structure changes to quaternary structure changes. The domain closure involves (local) motions of up to 2 A. There is one interdomain linkage and to a large degree the domain closure can be considered to operate by a hinge mechanism. There are, however, additional loop movements in both domains (the 80s and 240s loops).

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

References
L Stryer (1995). Biochemistry. New York, W H Freeman and Company. [Medline info for 1660136]
R C Stevens, J E Gouaux and W N Lipscomb (1990). Structural consequences of effector binding to the T state of aspartate carbamoyltransferase: crystal structures of the unligated and ATP- and CTP- complexed enzymes at 2.6 A resolution. Biochemistry. 29: 7691-7701. [Medline info for 91104727]
R C Stevens and W N Lipscomb (1992). A molecular mechanism for pyrimidine and purine nucleotide control of aspartate transcarbamoylase. Proc. Natl. Acad. Sci. 89: 5281-5285. [Medline info for 92302228]

Data and Graphics
Graphic-1 Graphic of the domain closure in the catalytic subunit courtesy of E S Huang.

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