2B1K

Crystal structure of E. coli CcmG protein

Summary for 2B1K

• Entry DOI: 10.2210/pdb2b1k/pdb
• Descriptor: Thiol:disulfide interchange protein dsbE (2 entities in total)
• Functional Keywords: c-terminal thioredoxin-like domain, n-terminal beta-sheet, fingerprint rigion, oxidoreductase
• Biological source: Escherichia coli
• Cellular location: Cell inner membrane; Single-pass membrane protein; Periplasmic side: P0AA86
• Total number of polymer chains: 1
• Total formula weight: 18953.46

Authors

Ouyang, N.,Gao, Y.G.,Hu, H.Y.,Xia, Z.X. (deposition date: 2005-09-15, release date: 2006-09-05, Last modification date: 2024-10-23)

Primary citation

Ouyang, N.,Gao, Y.G.,Hu, H.Y.,Xia, Z.X.
Crystal structures of E. coli CcmG and its mutants reveal key roles of the N-terminal beta-sheet and the fingerprint region
Proteins, 65:1021-1031, 2006

PubMed Abstract: CcmG, also designated DsbE, functions as a periplasmic protein thiol:disulfide oxidoreductase and is required for cytochrome c maturation. Here we report the crystal structures of Escherichia coli CcmG and its two mutants, P144A and the N-terminal fifty seven-residue deletion mutant, and two additional deletion mutants were studied by circular dichroism. Structural comparison of E. coli CcmG with its deletion mutants reveals that the N-terminal beta-sheet is essential for maintaining the folding topology and consequently maintaining the active-site structure of CcmG. Pro144 and Glu145 are key residues of the fingerprint region of CcmG. Pro144 is in cis-configuration, and it makes van der Waals interactions with the active-site disulfide Cys80-Cys83 and forms a C--H...O hydrogen bond with Thr82, helping stabilize the active-site structure. Glu145 forms a salt-bridge and hydrogen-bond network with other residues of the fingerprint region and with Arg158, further stabilizing the active-site structure. The cis-configuration of Pro144 makes the backbone nitrogen and oxygen of Ala143 exposed to solvent, favorable for interacting with binding partners. The key role of cis-Pro144 is verified by the P144A mutant, which contains trans-Ala144 and displays redox property changes. Structural comparison of E. coli CcmG with the recently reported structure of CcmG in complex with the N-terminal domain of DsbD reveals that Tyr141 undergoes conformational changes upon binding DsbD. A cis-proline located at the N-terminus of the first beta-strand of the betabetaalpha motif of the thioredoxin-like domain is a conserved structural feature of the thioredoxin superfamily.

PubMed: 17019698
DOI: 10.1002/prot.21184

Experimental method

X-RAY DIFFRACTION (1.9 Å)