Functional Regions Of The Regulatory Factor CCM1 Indispensable To The CO₂-limiting Stress Responses In Chlamydomonas reinhardtii

Abstract

Under the poor availability of inorganic carbon (CO₂, HCO₃^-, etc. :Ci) for photosynthesis, Chlamydomonas or cyanobacteria induce the active uptake systems for Ci within the cell (Carbon-concentrating mechanism :CCM). In Chlamydomonas, the regulatory factor CCM1 is indispensable to induce the CCM. In order to detect the CCM1 protein, anti-CCM1 antibody was generated using His-tagged CCM1. A protein band with a higher M.W. was detected in western blot analysis. Considering with the fact that the deduced M.W. of CCM1 was 70,073, some modifications of CCM1 were suggested. The expression of CCM1 was constitutive and independent of CO₂ concentration. Moreover, CCM1 has five Cys residues conserved in the zinc-finger domain. The strains expressing the modified CCM1 with D60H, D60C, D60V were created respectively. Since all the strains grew as in the case of wild type under the CO₂-limiting condition, it was suggested the Asp-60 is replaceable in the function of CCM1.