9atc

ATCASE Y165F MUTANT

spinqualitylabelsall models 9atc, resolution 2.40Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9atc is a 2 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: ZN Activity: Aspartate carbamoyltransferase, with EC number 2.1.3.2 Resources: FirstGlance, OCA, RCSB, PDBsum Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed 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. 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 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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