Phosphatase Subfamily PTPRG Tech Note
The gain of N-terminal Carbonic anhydrase (CA) domain
We found the origin of CA domain in a narrow-down approach by BLASTing the sequence of CA domain against different clades. We BLASTed the N-terminal CA domain sequence determined by CDD (1-275 of human PTPRG) against protein NR datasets, with the phylogeny as i) all eukaryotes, ii) animals except vertebrates, iii) deuterostomes except vertebrates and iv) vertebrates. In invertebrates, all of the hits have a single CA domain, rather than fn3 or phosphatase domain found in PTPRG. We found CA-containing PTPRG in almost all vertebrates (lamprey lacks CA domain due to the incomplete gene model). In sum, the CA domain was gained in vertebrates.