Mass Spectral Analysis of the Regulatory Factor CCM1, the Master Regulator of the Carbon-concentrating Mechanism in Chlamydomonas reinhardtii

Abstract

In conditions of CO₂-limiting stress, aquatic photosynthetic organisms induce active uptake systems for inorganic carbon (Ci) that enable the accumulation of Ci within the cell (Carbon-Concentrating Mechanism: CCM). In Chlamydomonas reinhardtii, the regulatory factor CCM1 (CIA5) is indispensable for induction of the CCM. Since the CCM1 was detected in fractions with high molecular weigh in vivo, it was possible that the CCM1 may form a complex with other unknown components. To know the molecular components of the putative CCM1 complex, the CCM1 was isolated by Tag-affinity purification method. It has been assumed that the CCM1-A and the CCM1-B were translated in vivo, because two types of the Ccm1 cDNA were isolated. Since the mass spectra derived from the CCM1-A were detected, the CCM1-A was translated in vivo. We discuss about the function of the CCM1 complex based on the findings by mass spectral analysis.