The Carbonic Anhydrase (CA) Domain of Arabidopsis Respiratory Complex I

EDUARDO JULIAN ZABALETA

Renaissance Tuscany Il Ciocco Lucca (Barga)

Conferencia; Gordon Conference-2017 CO2 Assimilation in Plants from Genome to Biome; 2017

Gordon Conference

Complex I is the main entrance of electrons from metabolism although there are many alternative entrances in Plant mitochondria. This complex is composed of 50 subunits in Arabidopsis. Here I show you a micrograph of Arabidopsis complex I showing the matrix arm and the membrane arm like other canonical complexes I from bacteria or mammals. However, in a variety of organisms except for animals and fungi, it contains an extra spherical domain, named CA (for carbonic anhydrase domain) which it was suggested to be composed of trimers of proteins sharing high homology with gamma ?type carbonic anhydrases. It is proposed a model for the in vivo composition of the CA domain which is different depending on the tissue. We estimate a % of complex I respect to WT on the different mutants in different stage of development. Thus, in immature embryos the main complex I should depend on CA1 while in leaves the main complex I should depend on CA2. This correlate as well with the proposed function of the CA domain, where CA2 dependent complex I is important for photorespiration while in immature embryos this process is not relevant. CA3 would stabilize the complex.At least four gamma carbonic anhydrases might form trimers named CA domain of mitochondrial Complex I.It is proposed that CA domain is linked to photorespiration as a bicarbonate transporter.CA proteins have a role as well in Complex I assembly.At least one CA and one CAL subunit is needed for complex I assembly and thus are required for normal embryogenesis.Exact localization of CA3 remains to be elucidated.