Abstract
The Β-type carbonic anhydrase (PtCA1) localizes as clustered particles on the girdle lamellae in the chloroplast of the marine diatom Phaeodactylum tricornutum . PtCA1 has been suggested to play an important role in CCM but mechanisms and physiological functions of PtCA1 are yet to be elucidated. PtCA1 forms cluster via a function of the amphipathetic helix at its C-terminus which occurs only in the chloroplast. This indicates that particle formation requires some stromal factors. As the first candidate, Rubisco was localized using GFP labeling but results unlikely co-localize with PtCA1. Immnopurecipitation assay revealed that PtCA1 antibody pull down only PtCA1 and its paralogue PtCA2. These results suggest that stromal factors mightn't be proteins or that interactions of particle components are fairly weak which doesn't fully function outside the stroma. The activity of recombinant PtCA1 was measured under conditions mimicking the stroma.
