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

Abstract

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.