9atc

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spinqualitylabelsall models 9atc, resolution 2.4Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

ATCASE Y165F MUTANT

Overview

Tyr 165 in the catalytic subunit of Escherichia coli aspartate, transcarbamoylase (ATCase, EC 2.1.3.2) forms an intersubunit hydrogen bond, in the T state with Glu 239 in the 240s loop of a second catalytic, subunit, which is broken in the T to R transition. Substitution of Tyr 165, by Phe lowers substrate affinity by approximately an order of magnitude, and alters the pH profile for enzyme function. We have determined the, crystal structure of Y165F at 2.4 A resolution by molecular replacement, using a wild-type T state structure as the probe, and refined it to an R, value of 25.2%. The Y165F mutation induces a global conformational change, that is in the opposite direction to the T to R transition and therefore, results in an extreme T state. The two catalytic trimers move closer by, approximately 0.14 A and rotate by approximately 0.2 degrees , in the, opposite direction to the T-->R rotation; the two domains of each, catalytic chain rotate by approximately 2.1 degrees, also in the opposite, direction to the T-->R transition; and the 240s loop adopts a new, conformation. Residues 229 to 236 shift by approximately 2.4 A so that the, active site is more open. Residues 237 to 244 rotate by approximately 24.1, degrees, altering interactions within the 240s loop and at the C1-C4 and, C1-R4 interfaces. Arg 167, a key residue in domain closure and, interactions with L-Asp, swings out from the active site to interact with, Tyr 197. This crystal structure is consistent with the functional, properties of Y165F, expands our knowledge of the conformational, repertoire of ATCase, and indicates that the canonical T state does not, represent an extreme.

About this Structure

9ATC is a Protein complex structure of sequences from Escherichia coli with ZN as ligand. Active as Aspartate carbamoyltransferase, with EC number 2.1.3.2 Full crystallographic information is available from OCA.

Reference

Intersubunit hydrogen bond acts as a global molecular switch in Escherichia coli aspartate transcarbamoylase., Ha Y, Allewell NM, Proteins. 1998 Nov 15;33(3):430-43. PMID:9829701

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