title: Structural characterization of the cytoplasmic pole of band 3 from bovine erythrocyte membranes.
abstract: In an earlier study, we found that chymotryptic digestion of band 3 isolated from bovine erythrocyte membranes produces a 38,000-Da fragment in nonaethyleneglycol-n-dodecylether solution or a 50,000-Da fragment in deoxycholate solution as a primary fragment [Makino et al. (1984) J. Biochem. 95, 1019]. In the present study, these fragments were purified in an aqueous medium without detergent and their structural properties were examined. Several lines of evidence showed that the 50,000-Da fragment constitutes the entire cytoplasmic pole of bovine band 3 and that the 38,000-Da fragment is a subfragment of the 50,000-Da fragment. The large fragment was suggested to be divided into two distinct regions, the 12,000- and 38,000-Da portions, differing in their conformational thermal stability. However, attempts to identify the 12,000-Da portion as an isolable segment were without success. The cytoplasmic pole was characterized as a dimer which adopts an elongated gross conformation with helix of approximately 35%. Treatment of the fragments with dimethylmaleic anhydride dissociated the dimers into the monomers, accompanied by a significant conformational change of the 38,000-Da portion. Comparative studies suggested that the cytoplasmic domain of bovine band 3 has structurally different region(s) from that of human band 3, though their gross conformation shows extensive similarity.
mesh_terms: D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000032:analysis*; D002417:Cattle; D002918:Chymotrypsin / Q000378:metabolism; D002942:Circular Dichroism; D003593:Cytoplasm / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000032:analysis*; D004912:Erythrocytes / Q000648:ultrastructure; D006801:Humans; D005779:Immunodiffusion; D008433:Mathematics; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D011487:Protein Conformation
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D010446:Peptide Fragments; D002918:Chymotrypsin