Abstract
Sec-translocase is an evolutionarily conserved protein translocation pathway and its functions are protein translocations, secretions and insertions. SecA,a motor protein, plays the important roles in translocations and couples ATP hydrolyzed energy with protein translocations. There is SecA homologue in plants, it functions in translocation from stroma into thylakoid lumen. Mycobacteria and Listeria possess two SecAs that distinguish its substrate proteins. But these substrates-distinction mechanisms are not known in plant cells.
Analysis of the complete genome sequences of a unicellular red alga Cyanidioschyzon merolae revealed two secA genes were encoded in the nuclear and plastid genomes respectively. These two secA genes were transcribed, and we suggested they possess some functions. These secAs were distinct phylogenetically. We demonstrated the homogeneous protein interactions in the nuclear and the plastid-encoded SecAs, and the heterogeneous interaction between the nuclear-encoded and the plastid-encoded SecA. And we demonstrated the optimal temperatures of its ATPase activities were obviously distinct. We discuss temperatures-distinction mechanism of C. merolae SecAs.
