Gamma carbonic anhydrase like complex interact with plant mitochondrial complex I

We report the identification by two hybrid screens of two novel similar proteins, called Arabidopsis thaliana gamma carbonic anhydrase like1 and 2 (At gamma CAL1 and At gamma CAL2), that interact specifically with putative Arabidopsis thaliana gamma Carbonic Anhydrase (At gamma CA) proteins in plant mitochondria. The interaction region that was located in the N-terminal 150 amino acids of mature At gamma CA and At gamma CA like proteins represents a new interaction domain. In vitro experiments indicate that these proteins are imported into mitochondria and are associated with mitochondrial complex I as At gamma CAs. All plant species analyzed contain both At gamma CA and At gamma CAL sequences indicating that these genes were conserved throughout plant evolution. Structural modeling of At gamma CAL sequences show a deviation of functionally important active site residues with respect to gamma CAs but could form active interfaces in the interaction with At gamma CAs. We postulate a CA complex tightly associated to plant mitochondrial complex.