Abstract
The β-type carbonic anhydrase (PtCA1) localizes as clustered particles at the surface of the girdle lamellae in the marine diatom Phaeodactylum tricornutum . Although, physiological roles of PtCA1 and its particle formation are not known, GFP analysis of N- or C-terminus truncation of the mature PtCA1 suggested that 263-282 region of C-terminus might be crucial for the particle formation of PtCA1. Hydrophobic Cluster Analysis for C-terminus (253-282) region of PtCA1 suggested that hydrophobic amino acids, M, L, I, L, and L could form a hydrophobic cluster on one face of the putative C-terminus α-helix. The hydrophilic residue, glutamic acid, was substituted for each or all of cluster-forming hydrophobic residues, M, L, I, L, and L in PtCA1-GFP fusion. As a result, the expressed GFP fusions dispersed with the stroma area without forming particles, indicating that these cluster-forming-residues play an essential role for the particle formation of PtCA1.
