STRUCTURE REQUIREMENTS FOR DISULFIDE BRIDGE SULFITOLYSIS OF OXIDIZED ESCHERICHIA-COLI THIOREDOXIN STUDIED BY FLUORESCENCE SPECTROSCOPY

Sulfitolysis of wild-type and four mutated Escherichia coli thioredoxi ns ([D26A]thioredoxin, [P34H]thioredoxin, [K36E]thioredoxin and endo-A rg(33a)-thioredoxin) has been investigated at millimolar concentration s of sulfite in the absence of protein-denaturing agents by fluorescen ce spectroscopy. Sulfitolysis of the single disulfide bridge of these proteins is associated with an increase in fluorescence emissions at 3 45 nm. Evaluation of the fluorescence emission spectra revealed that s ulfitolysis of thioredoxins is a homogenous process. The reactivities of the thioredoxins are determined by negatively charged (Asp26) or po sitively charged (Lys36) amino acid residues near the active site disu lfide bridge.