SDS-gel electrophoresis of ligand affinity-purified human IF-cobalamin receptor/cubilin and determination of its amino-terminal sequence. Elution of the receptor from porcine IF-cobalamin-Sepharose column loaded with Triton-X100–solubilized human renal cortex membranes was performed by changing the pH of the running buffer to 4.0 and adding 5 mmol/L EDTA to the buffer. The determined amino-terminal sequence of the 460-kD protein is indicated. Ten microliters of each fraction was loaded on a 4% to 16% polyacrylamide gel and run under reducing conditions.