Isolation and characterization of a cDNA coding for pea chloroplastic carbonic anhydrase

Using a polyclonal antibody generated against the purified pea (Pisum sativum) carbonic anhydrase (CA) monomeric species, we have isolated and characterized a cDNA coding for this enzyme. Protein sequence analysis was used to confirm the identity of the clone. The presence of a large transit peptide suggests that CA is transported into the chloroplast and then processed to the mature size of approximately 26 kilodaltons. Northern hybridization, using the CA cDNA as a probe of total leaf RNA, revealed a single transcript of 1.45 kilobase pairs. This transcript was not detected in RNA extracted from root or etiolated leaf tissue. Comparison of the deduced amino acid sequence with that of spinach CA showed approximately 68% identity over the length of the nascent protein but with greater similarity observed within the mature protein sequences. In addition, regions of the pea and spinach CA proteins were found to be significantly similar to the Escherichia coli cyanate permease.