Three-dimensional solution structure of the reduced form of Escherichia coli thioredoxin determined by nuclear magnetic resonance spectroscopy.
The three-dimensional solution structure of reduced (dithiol) thioredoxin from Escherichia coli has been determined with distance and dihedral angle constraints obtained from 1H NMR spectroscopy. Reduced thioredoxin has a well-defined global fold consisting of a central five-strand beta-sheet and three long helices. The beta-strands are packed in the sheet in the order beta 1 beta 3 beta 2 beta 4 beta 5, with beta 1, beta 3, and beta 2 parallel and beta 2, beta 4, and beta 5 arranged in an antiparallel fashion. Two of the helices connect strands of the beta-sheet: alpha 1 between beta 1 and beta 2 and alpha 2 between beta 2 and beta 3. Strands beta 4 and beta 5 are connected by a short loop that contains a beta-bulge. Strands beta 3 and beta 4 are connected by a long loop that contains a series of turn-like or 3(10) helical structures. The active site Cys-Gly-Pro-Cys sequence forms a protruding loop between strand beta 2 and helix alpha 2. The structure is very similar overall to that of oxidized (disulfide) thioredoxin obtained from X-ray crystal structure analysis but differs in the local conformation of the active site loop. The distance between the sulfurs of Cys 32 and Cys 35 increases from 2.05 A in the disulfide bridge to 6.8 +/- 0.6 A in the dithiol of reduced thioredoxin, as a result of a rotation of the side chain of Cys 35 and a significant change in the position of Pro 34. This conformational change has important implications for the mechanism of thioredoxin as a protein disulfide oxidoreductase.
Dyson
H J
HJ
Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
Gippert
G P
GP
Case
D A
DA
Holmgren
A
A
Wright
P E
PE
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001665:Binding Sites; D004220:Disulfides; D004926:Escherichia coli / Q000032:analysis*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D011487:Protein Conformation; D013879:Thioredoxins; D014961:X-Ray Diffraction
D001426:Bacterial Proteins; D004220:Disulfides; D013879:Thioredoxins