Abstract
Red cell membranes from ruminant animals contain a considerable amount of a 155-kDa glycoprotein (gp155) withmultiple membrane spans. A series of traditional biochemical experiments showed that the gp155 was linked to band3, anion exchanger 1 (AE1), and this gp155–band 3 complex in turn was associated to ankyrin through the binding ofband 3 to ankyrin. The gp155 is now identified as a member of the ABC transporter superfamily, ABCC4, based onthe result of the genome database searching and cloning of the gp155 cDNA. On the other hand, we examined themechanism for the endoplasmic reticulum–associated degradation of the mutant band 3 causative of the dominanthereditary spherocytosis in cattle, utilizing the artificial expression and detection of the proteins in HEK293 cells, anddemonstrated that the band 3 was associated with the cystic fibrosis transmembrane conductance regulator, CFTR(=ABCC7) in the endoplasmic reticulum. These findings indicate that band 3 may form hetero–oligomers with someisoforms of the ABC transporters.
