Cellular uptake of vitamin B: Role and fate of TCblR/CD320, the transcobalamin receptor.

Cellular uptake of vitamin B (cobalamin, Cbl) is mediated by a cell surface receptor (TCblR/CD320) that binds transcobalamin (TC) saturated with Cbl. TC is secreted by the vascular endothelium, has a relatively short half-life, binds Cbl with high affinity and presents the vitamin to the receptor for cellular uptake. Here we show binding and internalization of the TC-Cbl complex along with its' receptor (TCblR) in several human cell lines.