Vitamin B12 Research Today is a free monthly online journal that collates and summarizes the latest research about Vitamin B12, including details on cyanocobalamin, benefits, supplements, deficiency, side-effects, sources.

The binding properties of the human receptor for the cellular uptake of vitamin B12.

Quadros EV, Nakayama Y, Sequeira JM

Department of Biochemistry, SUNY-Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA. edward.quadros@downstate.edu

Cellular uptake of vitamin B(12) (cobalamin, Cbl) is mediated by a receptor expressed on the plasma membrane that binds transcobalamin (TC) saturated with Cbl and internalizes the TC-Cbl by endocytosis. A few reports have described the characterization of the receptor protein. However, many discrepancies have emerged in the functional and structural properties of the receptor and therefore, the identity and primary structure of this protein remains unconfirmed. In this report, we provide evidence of a 58 kDa monomeric protein as the likely receptor for the uptake of TC-Cbl and that the functional activity is not associated with a 72/144 kDa monomer/dimer with immunoglobulin Fc structural domain that has been purported to be the receptor in a number of publications.

Published 17 January 2005 in Biochem Biophys Res Commun, 327(4): 1006-10.
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