PDBsum entry 9atc

Transferase

PDB id: 9atc

Contents

Protein chains

310 a.a. *

146 a.a. *

Metals

_ZN

* Residue conservation analysis

PDB id:

9atc

Name:

Transferase

Title:

Atcase y165f mutant

Structure:

Aspartate transcarbamoylase. Chain: a. Engineered: yes. Mutation: yes. Aspartate transcarbamoylase. Chain: b. Engineered: yes. Mutation: yes

Source:

Escherichia coli. Organism_taxid: 562. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dodecamer (from PDB file)

Resolution:

2.40Å R-factor: 0.252 R-free: 0.344

Authors:

Y.Ha,N.M.Allewell

Key ref:

Y.Ha and N.M.Allewell (1998). Intersubunit hydrogen bond acts as a global molecular switch in Escherichia coli aspartate transcarbamoylase. Proteins, 33, 430-443. PubMed id: 9829701

Date:

26-Jun-98 Release date: 26-Jul-99

Protein chain

P0A786  (PYRB_ECOLI) -  Aspartate carbamoyltransferase catalytic subunit from Escherichia coli (strain K12)

Seq: 311 a.a.

Struc: 310 a.a.*

Protein chain

P0A7F3  (PYRI_ECOLI) -  Aspartate carbamoyltransferase regulatory chain from Escherichia coli (strain K12)

Seq: 153 a.a.

Struc: 146 a.a.

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: Chains A, B: E.C.2.1.3.2 - aspartate carbamoyltransferase.
• Pathway: Pyrimidine Biosynthesis
• Reaction: carbamoyl phosphate + L-aspartate = N-carbamoyl-L-aspartate + phosphate + H⁺

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

Proteins 33:430-443 (1998)

PubMed id: 9829701

Intersubunit hydrogen bond acts as a global molecular switch in Escherichia coli aspartate transcarbamoylase.

Y.Ha, N.M.Allewell.

ABSTRACT

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.