Chemical evidence for the difference between albumins from microsomes and serum and a possible precursor-product relationship

Immunologically isolated albumin from rat liver microsomes separates on DEAE-cellulose into almost equal proportions of an albumin-like protein and authentic albumin. Besides this similarity in immunological properties, both albumin species have almost the same molecular weight and amino acid composition. Furthermore, the amino acid sequences appear to be identical apart from an additional pentapeptide at the N-terminus of the albumin-like protein. It is suggested that the albumin-like protein represents a precursor which is converted to albumin by release of a pentapeptide from the N-terminus.