The isolation and functional identification of a protein from the human erythrocyte ‘ghost’

A protein, initially identified as a band on polyacrylamide-gel electrophoresis of erythrocyte ;ghosts', was isolated by selective extraction of ;ghosts' with EDTA solutions. The molecular weight of the polypeptide chain was estimated as 33000 and it represents approx. 5% of the membrane protein. The N-terminal sequence of the protein was established. Comparison with known protein sequences suggested that the protein might be the erythrocyte d-glyceraldehyde 3-phosphate dehydrogenase. This identification was confirmed by direct enzyme assay. It is suggested that this enzyme, which is strongly retained by erythrocyte ;ghosts' on haemolysis of erythrocytes, is unlikely to be an integral part of the structure of the erythrocyte membrane.