RUBISCO SUBUNIT BINDING-PROTEIN INCREASES THE SOLUBILITY OF RUBISCO LARGE SUBUNIT INVITRO

The effect of Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase, EC 4.1.1.39) subunit binding protein (BP) on the solubility of Rubisco large subunits was studied in an in vitro experiment, using Rubisco and BP preparations purified from wheat seedlings (Triticum aestivum). The Rubisco molecule was dissociated into subunits at pH 5 in the absence and presence of BP. In the absence of BP the large subunits aggregated, and did not redissolve in neutral buffer without the addition of detergent and mercaptoethanol. Where BP was present during the dissociation of the Rubisco, large subunits associated with the BP complex, and showed increased solubility in neutral buffer. The result suggests that specific binding of large subunits to the BP complex reduces the tendency of these polypeptides to associate incorrectly with one another.