(R-L) Scientists Erin Bertrand and Mak Saito applied proteomics to discover CBA1. (Photo: Tom Kleindinst/WHOI)
Scientists discover smart protein algae that absorbs B12
Monday, June 04, 2012, 06:00 (GMT + 9)
Scientists have exposed a key biochemical component through which marine algae can thrive: a previously unknown protein that pulls vitamin B12, an essential but scarce nutrient, out of seawater.
A team of researchers from Woods Hole Oceanographic Institution (WHOI) and the J Craig Venter Institute found a protein they described as "the B12 claw" while examining algal cultures and seawater samples from the Southern Ocean off Antarctica.
The findings were published on 31 May in Proceedings of the National Academy of Sciences.
Many algae -- as well as humans and multiple animals -- need to acquire B12 from their diet, as their bodies do not manufacture it themselves. Only certain single-celled bacteria and archaea can synthesize B12, which is also known as cobalamin, on their own.
The researchers found a protein within the algae's cell walls that appears to function by binding B12 in the ocean and helping to draw it into the cell. When B12 supplies are in short supply, algae make up for it by producing more of the protein, now officially known as cobalamin acquisition protein 1, or CBA1.
|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. (Source: Erin Bertrand, Woods Hole Oceanographic Institution and J. Craig Venter Institute)
Algae set the food chain in motion and have critical impacts on the marine food web and the planet’s climate. Marine algae absorb huge amounts of carbon dioxide from the air through photosynthesis. When algae die or are consumed, some of the carbon ends up sinking to the ocean floor, from which it cannot re-enter the atmosphere.
The discovery of CBA1 also makes possible industrial and therapeutic applications.
As CBA1 is essential for marine algae growth, it could help researchers find how to promote the growth of algae used to generate biofuels. Further, being able to manipulate the B12 biochemical pathways of beneficial or harmful microbes could lead to the development of antibiotic or antifungal medicines.
In order to discover CBA1, Erin Bertrand, a graduate student in the MIT/WHOI Joint Programme in Oceanography, and her advisor, WHOI biogeochemist Mak Saito, employed an approach frequently used in biomedical research but only recently applied to marine science. It is called proteomics, or the study of the proteins that organisms make so they can function in their environment and adapt to shifting conditions.
By Natalia Real