Gamma carbonic anhydrases in plant mitochondrial complex I

PARISI, G.; PERALES, M.; FORNASARI, S.; COLANERI, A.; GONZÁLEZ-SCHAIN, N.; GÓMEZ-CASATI, D.; ZIMMERMANN, S.; ECHAVE, J.; FERRY, J. G.; EDUARDO JULIAN ZABALETA

PLANT MOLECULAR BIOLOGY

Amsterdam

Año: 2004 vol. 55 p. 193 - 207

0167-4412

Three genes from Arabidopsis thaliana with high sequence similarity to gamma carbonic anhydrase (cCA), aZn containing enzyme from Methanosarcina thermophila (CAM), were identified and characterized. Evolutionaryand structural analyses predict that these genes code for active forms of cCA. Phylogeneticanalyses reveal that these Arabidopsis gene products cluster together with CAM and related sequencesfrom a and c proteobacteria, organisms proposed as the mitochondrial endosymbiont ancestor. Indeed,in vitro and in vivo experiments indicate that these gene products are transported into the mitochondria asoccurs with several mitochondrial protein genes transferred, during evolution, from the endosymbioticbacteria to the host genome. Moreover, putative CAM orthologous genes are detected in other plants andgreen algae and were predicted to be imported to mitochondria. Structural modeling and sequence analysisperformed in more than a hundred homologous sequences show a high conservation of functionallyimportant active site residues. Thus, the three histidine residues involved in Zn coordination (His 81, 117and 122), Arg 59, Asp 61, Gin 75, and Asp 76 of CAM are conserved and properly arranged in the activesite cavity of the models. Two other functionally important residues (Glu 62 and Glu 84 of CAM) arelacking, but alternative amino acids that might serve to their roles are postulated. Accordingly, we proposethat photosynthetic eukaryotic organisms (green algae and plants) contain cCAs and that these enzymescodified by nuclear genes are imported into mitochondria to accomplish their biological function.IntroductionCarbonic anhydrase (CA; carbonate dehydratase,carbonate hydro-lyase, EC 4.2.1.1) is a zinc-containingenzyme that catalyzes the interconversionof CO2