Chemical Cross-Linking Between Fructose-1,6-Bisphosphatase and Thioredoxin F

Fructose-1,6-bisphosphatase (FBPase), a key enzyme in the regulation of the reductive pentose-phosphate cycle, is modulated by thioredoxin f (Trx f), that links photosynthetic electron transport to the enzyme (1). Both proteins form an associated complex that is important to the reductive activation. This protein-protein interaction is favoured at low ionic strength and a restricted pH range (2). Earlier results suggested that the regulatory site preceding region in the FBPase, which shows a high concentration of acid residues, is the docking point (3,4) and that, conversely, amino residues from Trx fare likely to be involved in the complex formation (5).