Abstract
RuBisCO is a key enzyme that catalyzes the addition of CO2 to ribulose-1,5-bisphosphate (RuBP) and produces two molecules of 3-phosphoglycerate (3-PGA). This enzyme is localized in the stroma of plastids and consists of two octamers of large subunit (encoded by the rbcL gene) and small subunit (encoded by the rbcS gene).
Cyanidioschyzon merolae, a unicellular rhodophytes contains an operon that is constituted of rbcL, rbcS and cbbX in a tandem array. The cbbX genes are not found in the chlorophytes, glaucophytes and cyanobacteria but are detected in some kinds of proteobacteria. Phylogenetic tree inferred from RbcLs indicates that RbcL of rhodophytes are more closely related to those of β-proteobacteria than those of non-rhodopyte plants or cyanobacteria. Interestingly, a cbbX homologue is also encoded in the cell nucleus of C. merolae. In this study, we performed functional analysis of the plastid and nuclear CbbX proteins and discussed the relationship between two CbbXs.
