Fatty Acids in M and N Blood Group Substances

Abstract

THE M and N blood group substances, obtained from human erythrocytes by phenol–water extraction, have been shown to be glycoproteins¹. They are polydisperse in the ultracentrifuge and have an average molecular weight of 5 × 10⁵–10⁶ (ref. 1). Morawiecki found that M and N mucoids were dissociated by detergents into uniform sub-units of molecular weight 30,000 (ref. 2), and suggested that the sub-units were kept in aggregates in water solution by hydrophobic bonds. The formation of hydrophobic bonds could be explained by an assymmetric distribution of the hydrophilic oligosaccharide side chains over the polypeptide “backbone”. Products of proteolytic degradation of M and N substances were known to be easily separated into two fractions, distinctly different in the content of sugar components³. Further proof of an assymmetric distribution of sugars in M and N mucoids was provided by the formation of the precipitate when treated with pronase⁴. The precipitate, containing many fewer sugar components than soluble glycopeptides, was probably formed from the more hydrophobic central part of the micelles.