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Images: Scientists Discover the "Vitamin B12 Claw"

For her Ph.D. research in the MIT/WHOI Joint Program in Oceanography, Erin Bertrand (right) studied how marine phytoplankton get, use, and compete for nutrients in the ocean. She worked her advisor, WHOI marine biogeochemist Mak Saito (left), whose lab group has been working to advance techniques using proteomics to study critical proteins in the marine environment. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

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)

An epifluorescence micrograph of a marine alga indicates that the cobalamin acquisition protein 1 (tagged with a light green fluorescent label) is associated with the outside of the cell wall, where it appears to facilitate bringing in vitamin B12 from the ocean into the cell. Red indicates cholorophyll. (Chris Dupont, J. Craig Venter Institute)