PDBsum entry 1v57

Isomerase

PDB id: 1v57

Contents

Protein chains

229 a.a. *

Ligands

SO4 ×4

Waters ×509

* Residue conservation analysis

PDB id:

1v57

Name:

Isomerase

Title:

Crystal structure of the disulfide bond isomerase dsbg

Structure:

Thiol:disulfide interchange protein dsbg. Chain: a, b. Synonym: dsbg disulfide bond isomerase. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 562. Gene: dsbg. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Biol. unit:

Tetramer (from PDB file)

Resolution:

2.00Å R-factor: 0.200 R-free: 0.232

Authors:

B.Heras,M.A.Edeling,H.J.Schirra,S.Raina,J.L.Martin

Key ref:

B.Heras et al. (2004). Crystal structures of the DsbG disulfide isomerase reveal an unstable disulfide. Proc Natl Acad Sci U S A, 101, 8876-8881. PubMed id: 15184683 DOI: 10.1073/pnas.0402769101

Date:

21-Nov-03 Release date: 29-Jun-04

Protein chains

P77202  (DSBG_ECOLI) -  Thiol:disulfide interchange protein DsbG from Escherichia coli (strain K12)

Seq: 248 a.a.

Struc: 229 a.a.

DOI no: 10.1073/pnas.0402769101

Proc Natl Acad Sci U S A 101:8876-8881 (2004)

PubMed id: 15184683

Crystal structures of the DsbG disulfide isomerase reveal an unstable disulfide.

B.Heras, M.A.Edeling, H.J.Schirra, S.Raina, J.L.Martin.

ABSTRACT

Dsb proteins control the formation and rearrangement of disulfide bonds during the folding of secreted and membrane proteins in bacteria. DsbG, a member of this family, has disulfide bond isomerase and chaperone activity. Here, we present two crystal structures of DsbG at 1.7and 2.0-A resolution that are meant to represent the reduced and oxidized forms, respectively. The oxidized structure, however, reveals a mixture of both redox forms, suggesting that oxidized DsbG is less stable than the reduced form. This trait would contribute to DsbG isomerase activity, which requires that the active-site Cys residues are kept reduced, regardless of the highly oxidative environment of the periplasm. We propose that a Thr residue that is conserved in the cis-Pro loop of DsbG and DsbC but not found in other Dsb proteins could play a role in this process. Also, the structure of DsbG reveals an unanticipated and surprising feature that may help define its specific role in oxidative protein folding. Thus, the dimensions and surface features of DsbG show a very large and charged binding surface that is consistent with interaction with globular protein substrates having charged surfaces. This finding suggests that, rather than catalyzing disulfide rearrangement in unfolded substrates, DsbG may preferentially act later in the folding process to catalyze disulfide rearrangement in folded or partially folded proteins.

Selected figure(s)

Figure 1.
Fig. 1. Structure of DsbG. (a) Crystal structure of the DsbG homodimer. (b) Each DsbG monomer consists of an N-terminal dimerization domain (blue), a linker helix (gray), and a C-terminal catalytic domain that has a TRX fold (pink). The active-site disulfide is shown in green. (c) Interaction between the two V-shaped DsbG homodimers (blue and gray) found in the crystal structure. The asymmetric unit contains one blue subunit and one gray subunit. The biological dimer (two blue or two gray subunits) is generated by applying crystallographic symmetry, as indicated by an arrow. (d) Stereoview of interactions with the Cys at the active site of reduced DsbG (synchrotron data). Figures were generated with MOLSCRIPT (32).

Figure 3.
Fig. 3. Comparison of oxidized and reduced Dsb active sites by schematic representation showing interactions at the active sites of DsbG, DsbC, and DsbA in the oxidized and reduced forms. Covalent bonds (gray), hydrogen bonds (dotted line), and proposed destabilizing interactions (black) are shown. For comparison with the Thr interaction in the DsbG and DsbC structures, the position of Val-150 is indicated. However, the distance between Cys-30 of DsbA and Val-150 is 3.7-4.2 Å in oxidized DsbA and 4.5-4.6 Å in reduced DsbA.

Figures were selected by the author.