The glycoprotein transcobalamin 1 (TCN1 aka haptocorrin, HC, TCI) binds correnoids, biologically inactive analogs of cobalamin (Cbl). The resulting complexes are cleared rapidly from the blood by hepatocytes and excreted in the urine and bile (Kolhouse & Allen 1977). Structural studies by Furger et al. (2013) and Alam et al. (2016) suggest mechanisms for the differential binding of Cbl over other correnoids by TCN2 in contrast to the broad correnoid specificity of TCN1, consistent with a role for the latter in scavenging and mediating the hepatobiliary excretion of corrinoids.
molecular sequestering activity of TCN1 [extracellular region]