Introduction of an intramolecular crosslink at the active site of glyceraldehyde 3-phosphate dehydrogenase

Reaction of rabbit muscle apo-glyceraldehyde 3 -phosphate dehydrogenase with one mole of 1, 5-difluoro, 2, 4-dinitrobenzene per mole of enzyme protomer brings about total loss of enzymatic activity and concomitant introduction of covalent intramolecular crosslinks at the active site of the enzyme. Following peptic digestion, a crosslinked couple of peptides was purified and found to have the structure:

The crosslinked cysteine and lysine residues, though some 32 amino acid residues apart in the primary sequence, may approach each other to a distance of 5–6 Å in the three dimensional structure of the enzyme.