Three-dimensional structure of thioredoxin induced by bacteriophage T4.

The three-dimensional structure of thioredoxin from bacteriophage T4 has been determined from a 2.8-angstrom resolution electron density map. Phase angles for this map were determined from one heavy atom derivative and anomalous differences from cadmium in the native crystals. The molecule of 87 amino acid residues is built up from two simple folding units; a betaalphabeta unit from the amino end of the chain and a betabetaalpha unit from the carboxyl end. This structure is similar to that of thioredoxin from Escherichia coli in spite of their completely different amino acid sequences. The redox-active S--S bridge is part of a protrusion of the molecule as in E. coli thioredoxin, but with quite different surroundings. The structural differences in this region have been correlated to differences in specificity towards the enzyme ribonucleotide reductase from different species.