The carbonic anhydrase domain of plant mitochondrial complex I

The mitochondrial NADH dehydrogenase complex (complex I) consists of several functional domains which independently arose during evolution. In higher plants, it contains an additional domain which includes proteins resembling gamma-type carbonic anhydrases. The Arabidopsis genome codes for five complex I-integrated gamma-type carbonic anhydrases (CA1, CA2, CA3, CAL1, CAL2), but only three copies of this group of proteins form an individual extra domain. Biochemical analyses revealed that the domain is composed of one copy of either CAL1 or CAL2 plus two copies of the CA1/CA2 proteins. Thus, the carbonic anhydrase domain can have six distinct subunit configurations. Single and double mutants with respect to the CA/CAL proteins were employed to genetically dissect the function of the domain. New insights into complex I biology in plants will be reviewed and discussed.