A Structure-Function Analysis of BtuB, the E.Coli . Vitamin B 12 Outer Membrane Transport Protein

Vitamin B12 or cobalamin is a member of a group of compounds known as the corrinoids which are the most complex, nonpolymeric molecules so far found in nature. They exist in trace amounts throughout the natural world, usually within the concentration range lxl0-9 to 1x10-15 (Bradbeer, 1982). Vitamin B12 is found in virtually all animal tissues to a greater or lesser degree, its source being ingested tissue or synthesis by gut flora.