Abstract
The coccolithophorid Emiliania huxleyi, a marine unicellular calcifying alga, produces mineralized scales called coccoliths by intracellular calcification. The process of calcification was not fully understood due to the lack of the information of proteins associated with the calcification.
We found that the calcification was promoted under phosphate-depleted conditions and low-temperature conditions and a protein which has an apparent molecular mass of 32-kDa was specifically synthesized under the conditions. We purified the protein and determined its N-terminal sequence. From the searching expressed-sequence-tag (EST) database, we found the sequence in the protein which has a highly conserved FK506-binding protein domain (FKBP), an EF-hand motif and an endoplasmic reticulum (ER) retention sequence. Because the deduced molecular mass of the protein was 20.4 kDa, the protein might be post-translationally modified in vivo. Mechanisms of the calcification may be elucidated by analyses of the functions of the protein.
