Enhanced CO2/O2 specificity of a site-directed mutant of ribulose-bisphosphate carboxylase/oxygenase.
The CO2/O2 specificity factor of ribulose-bisphosphate carboxylase/oxygenase partially determines the efficiency of photosynthetic carbon assimilation. Heretofore, engineered alterations of the enzyme have only decreased the selectivity for CO2 utilization. We show that alanyl replacement of active-site Ser-368 of the Rhodospirillum rubrum carboxylase enhances the carboxylation selectivity approximately 1.6-fold over the wild-type level. This enhancement reflects a greater relative decline in oxygenase efficiency than in carboxylase efficiency. In contrast to wild-type enzyme, the carboxylase activity of the Ser-368 mutant protein is not perceptibly inhibited by O2, perhaps indicative of a change in rate-limiting steps in the overall reaction pathway.
Harpel
M R
MR
Protein Engineering Program, Oak Ridge National Laboratory, Tennessee 37831-8077.
Hartman
F C
FC
D002245:Carbon Dioxide / Q000378:metabolism*; D015870:Gene Expression; D016297:Mutagenesis, Site-Directed; D010100:Oxygen / Q000378:metabolism*; D012247:Rhodospirillum rubrum / Q000201:enzymology; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D013379:Substrate Specificity
D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D010100:Oxygen