Crystal structure of the DsbA protein required for disulphide bond formation in vivo

Abstract

Proteins that contain disulphide bonds are often slow to fold in vitro because the oxidation and correct pairing of the cysteine residues is rate limiting. The folding of such proteins is greatly accelerated in Escherichia coli by DsbA, but the mechanism of this rate enhancement is not well understood. Here we report the crystal structure of oxidized DsbA and show that it resembles closely the ubiquitous redox protein thioredoxin, despite very low sequence similarity. An important difference, however, is the presence of another domain which forms a cap over the thioredoxin-like active site of DsbA. The redox-active disulphide bond, which is responsible for the oxidation of substrates, is thus at a domain interface and is surrounded by grooves and exposed hydrophobic side chains. These features suggest that DsbA might act by binding to partially folded polypeptide chains before oxidation of cysteine residues.

The uncharged surface features surrounding the active site ofEscherichia coliDsbA are conserved and are implicated in peptide binding

“…The root-mean-square deviation (RMSD) between the two structures for all Ca atoms of both munomers is 0.15 A. As described previously (Martin et al, 1993a), the structure of DsbA consists of a thioredoxin fold (residues 1-62 and 139-188) with a helical domain insert (residues 63-138).…”

The protein disulphide-isomerase family: unravelling a string of folds

“…This large family accommodates thioredoxin-like, glutaredoxin-like and PDI-like proteins, as well as members of the bacterial Dsb family [14,26,42,43], all of which contain one or more copies of the highly conserved thioredoxin fold, i.e. a β-α-β-α-β-α-β-β-α structure (as shown in Figures 1 and 2) encompassing a reactive -Cys-Xaa-Xaa-Cys-tetrapeptide [9,34,[44][45][46].…”

The Acidic Nature of the CcmG Redox-Active Center Is Important for CytochromecMaturation inEscherichia coli

“…The redox-active center of CcmG is relatively acidic (7) compared to other TRX-like oxidoreductases, including TRX (13), DsbA (20), DsbC (21), and the closest structural relative to CcmG, TlpA (2). Three acidic residues in CcmG, of which two are exposed to solvent (Asp97 and Glu158 in B. japonicum CcmG) and one is partly buried (Glu98 in B. japonicum CcmG), contribute to the acidic redoxactive center.…”