PDBsum entry 2g6c

Transferase

PDB id: 2g6c

Contents

Protein chain

332 a.a. *

Ligands

SO4

SN0

_CP

Waters ×44

* Residue conservation analysis

Obsolete entry

PDB id:

2g6c

Name:

Transferase

Title:

Crystal structure of x. Campestris n-acetylornithine transcarbamylase e92v mutant complexed with carbamoyl phosphate and n-succinylnorvaline

Structure:

N-acetylornithine carbamoyltransferase. Chain: a. Synonym: aotcase. Engineered: yes. Mutation: yes

Source:

Xanthomonas campestris. Organism_taxid: 339. Gene: argf'. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Resolution:

2.81Å R-factor: 0.207 R-free: 0.258

Authors:

D.Shi,X.Yu,L.Roth,H.Morizono,N.M.Allewell,M.Tuchman

Key ref:

D.Shi et al. (2007). A single mutation in the active site swaps the substrate specificity of N-acetyl-L-ornithine transcarbamylase and N-succinyl-L-ornithine transcarbamylase. Protein Sci, 16, 1689-1699. PubMed id: 17600144 DOI: 10.1110/ps.072919907

Date:

24-Feb-06 Release date: 06-Mar-07

Protein chain

Q8P8J2  (AOTC_XANCP) -  N-acetylornithine carbamoyltransferase from Xanthomonas campestris pv. campestris (strain ATCC 33913 / DSM 3586 / NCPPB 528 / LMG 568 / P 25)

Seq: 339 a.a.

Struc: 333 a.a.*

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

Enzyme reactions

• Enzyme class: E.C.2.1.3.9 - N-acetylornithine carbamoyltransferase.
• Reaction: N₂-acetyl-L-ornithine + carbamoyl phosphate = N₂-acetyl-L-citrulline + phosphate + H⁺

N(2)-acetyl-L-ornithine (Bound ligand (Het Group name = CP) corresponds exactly) + carbamoyl phosphate = N(2)-acetyl-L-citrulline + phosphate + H(+)

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

reference

DOI no: 10.1110/ps.072919907

Protein Sci 16:1689-1699 (2007)

PubMed id: 17600144

A single mutation in the active site swaps the substrate specificity of N-acetyl-L-ornithine transcarbamylase and N-succinyl-L-ornithine transcarbamylase.

D.Shi, X.Yu, J.Cabrera-Luque, T.Y.Chen, L.Roth, H.Morizono, N.M.Allewell, M.Tuchman.

ABSTRACT

Transcarbamylases catalyze the transfer of the carbamyl group from carbamyl phosphate (CP) to an amino group of a second substrate such as aspartate, ornithine, or putrescine. Previously, structural determination of a transcarbamylase from Xanthomonas campestris led to the discovery of a novel N-acetylornithine transcarbamylase (AOTCase) that catalyzes the carbamylation of N-acetylornithine. Recently, a novel N-succinylornithine transcarbamylase (SOTCase) from Bacteroides fragilis was identified. Structural comparisons of AOTCase from X. campestris and SOTCase from B. fragilis revealed that residue Glu92 (X. campestris numbering) plays a critical role in distinguishing AOTCase from SOTCase. Enzymatic assays of E92P, E92S, E92V, and E92A mutants of AOTCase demonstrate that each of these mutations converts the AOTCase to an SOTCase. Similarly, the P90E mutation in B. fragilis SOTCase (equivalent to E92 in X. campestris AOTCase) converts the SOTCase to AOTCase. Hence, a single amino acid substitution is sufficient to swap the substrate specificities of AOTCase and SOTCase. X-ray crystal structures of these mutants in complexes with CP and N-acetyl-L-norvaline (an analog of N-acetyl-L-ornithine) or N-succinyl-L-norvaline (an analog of N-succinyl-L-ornithine) substantiate this conversion. In addition to Glu92 (X. campestris numbering), other residues such as Asn185 and Lys30 in AOTCase, which are involved in binding substrates through bridging water molecules, help to define the substrate specificity of AOTCase. These results provide the correct annotation (AOTCase or SOTCase) for a set of the transcarbamylase-like proteins that have been erroneously annotated as ornithine transcarbamylase (OTCase, EC 2.1.3.3).

Selected figure(s)

Figure 1.
Figure 1. N-acetylnorvaline or N-succinylnorvaline binding of SOTCase or AOTCase mutants. (A--D) Contours of the electron density

Figure 5.
Figure 5. A schematic diagram representing the classification of four

The above figures are reprinted by permission from the Protein Society: Protein Sci (2007, 16, 1689-1699) copyright 2007.

Figures were selected by an automated process.