Dependence of catalysis and CO2/O2 specificity of Rubisco on the carboxy-terminus of the large subunit at different temperatures

Variations in length and charge of the C-terminus of the Rubisco large subunit (L) can be seen in L from different phylogenetic lineages. We examined the catalytic parameters of Rubisco from higher plants and from engineered Synechococcus rbcL in relation to differences in the C-terminus. Among three selected higher plants, spinach, wheat, and Flaveria pringlei, spinach Rubisco with the shortest C-tail extension (D-473 + 2) showed the lowest temperature response. The response of Rubisco from wheat (D-473 + 4) was intermediate, and the enzyme from F. pringlei (D-473 + 12) displayed the highest temperature response in terms of V^sub max^ for the carboxylase reaction. This observation was further investigated in a model system: the temperature-response for carboxylation was enhanced after lengthening the C-terminus of the Synechococcus large subunit protein by two amino acid residues (DK). The results point towards the length of the C-terminus as an additional factor for controlling Rubisco activity, especially as an adaptation that widens the temperature range in which the enzyme can function. Longer C-termini, we suggest, could establish additional interactions with the protein surface.[PUBLICATION ABSTRACT]