Cobalamin acquistion protein 1 (CBA1) appears to operate by binding vitamin B12 in the ocean and bringing it into algal cells, where the vitamin is needed to create another enzyme essential for growth, methionine synthase (MetH). However, when B12 supplies are scarce, algae produce more CBA1 to try to obtain more B12, and, as a back-up, some algae must resort to creating another enzyme, MetE, which can replace MetH but is far less efficient. (Erin Bertrand, Woods Hole Oceanographic Institution and J. Craig Venter Institute)[back]
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