Mutation of asparagine 111 of rubisco from Rhodospirillum rubrum alters the carboxylase/oxygenase specificity.
The conserved asparagine 111 of ribulose-1,5-bisphosphate carboxylase/oxygenase from the photosynthetic bacteria Rhodospirillum rubrum was identified as a candidate for a side-chain that might be involved in the carboxylase/oxygenase specificity. It was replaced by site-directed mutagenesis with aspartic acid, leucine, glutamine or glycine residues. The mutant enzymes exhibit a very low carboxylase activity compared with the wild-type enzyme. The values of Km(RuBP) and kcat for Asn111----Gly, the most active mutant, are 420 microM and 0.034 s-1, compared with 13 microM and 3.0 s-1 for wild-type. The mutation of Asn111----Gly causes a more than tenfold decrease in the CO2/O2 specificity factor, tau, tau Asn111----Gly = 0.56 and tau wild-type = 6. 7. This is the first reported change in rubisco specificity by a single site-directed mutation alone and suggests a target for future protein engineering studies.[1]References
- Mutation of asparagine 111 of rubisco from Rhodospirillum rubrum alters the carboxylase/oxygenase specificity. Chène, P., Day, A.G., Fersht, A.R. J. Mol. Biol. (1992) [Pubmed]
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