Abstract
The 35kDa glycoprotein, glycophorin A (GPA), is the most abundant sialylated glycoprotein (≈0.2-1x106 copies per cell) on human red blood cells (1). It was the first membrane protein to be fully sequenced and is still one of the best studied single pass transmembrane proteins, comprising 131 amino acids (2, 3). What has fascinated glycobiologists about GPA is its extensively glycosylated extracellular domain, and the extraordinarily high sialic acid content (4-9).
There are several recent reviews on the human erythrocyte glycophorins that cover the molecular characterisation of the GPA gene, its variants (10) and the structure and function of GPA antigens (1). The purpose of this review is to summarise studies associated with the glycosylation of GPA, the sites of glycosylation, the types of sugars present on GPA and its variants, and the possible role(s) that the carbohydrates may play in the function of GPA. In addition we review the advances in technology associated with glycosylation site identification, particularly heavily O-glycosylated domains typical of GPA and mucins (11).
