PDBsum entry 2rbh

Transferase

PDB id: 2rbh

Contents

Protein chains

169 a.a. *

Waters ×70

* Residue conservation analysis

PDB id:

2rbh

Name:

Transferase

Title:

Gamma-glutamyl cyclotransferase

Structure:

Gamma-glutamyl cyclotransferase. Chain: a, b. Synonym: uncharacterized protein c7orf24. Engineered: yes. Mutation: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: c7orf24, ggct. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Resolution:

2.10Å R-factor: 0.203 R-free: 0.255

Authors:

A.J.Oakley,P.G.Board

Key ref:

A.J.Oakley et al. (2008). The identification and structural characterization of C7orf24 as gamma-glutamyl cyclotransferase. An essential enzyme in the gamma-glutamyl cycle. J Biol Chem, 283, 22031-22042. PubMed id: 18515354 DOI: 10.1074/jbc.M803623200

Date:

19-Sep-07 Release date: 02-Oct-07

Protein chains

O75223  (GGCT_HUMAN) -  Gamma-glutamylcyclotransferase from Homo sapiens

Seq: 188 a.a.

Struc: 169 a.a.*

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

Enzyme reactions

• Enzyme class: E.C.4.3.2.9 - gamma-glutamylcyclotransferase.
• Reaction: an alpha-(gamma-L-glutamyl)-L-amino acid = 5-oxo-L-proline + an L-alpha- amino acid

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

Key reference

DOI no: 10.1074/jbc.M803623200

J Biol Chem 283:22031-22042 (2008)

PubMed id: 18515354

The identification and structural characterization of C7orf24 as gamma-glutamyl cyclotransferase. An essential enzyme in the gamma-glutamyl cycle.

A.J.Oakley, T.Yamada, D.Liu, M.Coggan, A.G.Clark, P.G.Board.

ABSTRACT

The hypothetical protein C7orf24 has been implicated as a cancer marker with a potential role in cell proliferation. We have identified C7orf24 as gamma-glutamyl cyclotransferase (GGCT) that catalyzes the formation of 5-oxoproline (pyroglutamic acid) from gamma-glutamyl dipeptides and potentially plays a significant role in glutathione homeostasis. In the present study we have identified the first cDNA clones encoding a gamma-glutamyl cyclotransferase. The GGCT gene is located on chromosome 7p14-15 and consists of four exons that span 8 kb. The primary sequence is 188 amino acids in length and is unlike any protein of known function. We crystallized functional recombinant gamma-glutamyl cyclotransferase and determined its structure at 1.7 A resolution. The enzyme is a dimer of 20,994-Da subunits. The topology of GGCT is unrelated to other enzymes associated with cyclotransferase-like activity. The fold was originally classified as "BtrG-like," a small family that only includes structures of hypothetical proteins from Mus musculus, Escherichia coli, Pyrococcus horikoshii, and Arabidopsis thaliana. Since this is the first member of this family with a defined function, we propose to refer to this structure as the gamma-glutamyl cyclotransferase fold. We have identified a potential active site pocket that contains a highly conserved glutamic acid (Glu(98)) and propose that it acts as a general acid/base in the reaction mechanism. Mutation of Glu(98) to Ala or Gln completely inactivates the enzyme without altering the overall fold.

Selected figure(s)

Figure 4.
Stereo diagrams of GGCT centered on the putative active site. Shown are stereo diagrams of the proposed active site regions of wild type GGCT (A) and E98A (B) and E98Q (C) mutants. Residues lining the pocket are rendered in stick form. The final 2 mF[o]- DF[c] electron density maps are rendered in chicken wire form in orange. All electron density maps are contoured at 1σ. WT, wild type.

Figure 5.
The structure and topology of GGCT. A, schematic diagrams showing the GGCT dimer. Orthogonal views are shown. Atoms of Glu^98 are represented as spheres. β-Strands are yellow, α-helices are purple, and 3[10] helices are green. B, schematic diagram of the GGCT monomer with secondary structure elements labeled. C, topology diagram of the GGCT monomer. β-Sheet interactions are indicated with black boxes. A red box indicates the interdimer β-sheet interaction. The wrapping of the central β-sheet to form a barrel is indicated by a faint representation of strands β2 and β4.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2008, 283, 22031-22042) copyright 2008.

Figures were selected by the author.

Author's comment

In a subsequent study we have shown that there are at least 3 major protein families with this fold and the human equivalent of the mouse structure shown in figure 9 catalyses a gamma-glutamylamine cyclotransferase reaction that specifically breaks gamma -glutamyl-epsilon -lysine peptide bonds.
Identification and characterization of {gamma}-glutamylamine cyclotransferase: An enzyme responsible for {gamma}-glutamyl-{epsilon}-lysine catabolism. Aaron J. Oakley, Marjorie Coggan, and Philip G. Board J. Biol. Chem. published 28 January 2010, 10.1074/jbc.M109.082099 http://www.jbc.org/cgi/content/abstract/M109.082099v1?papetoc
Philip Board