Reactive sulfhydryl groups of the band 3 polypeptide from human erythroycte membranes. Location in the primary structure

• Published in: The Journal of biological chemistry Vol. 254; no. 13; pp. 6144 - 6150
• Main Authors: Rao, A, Reithmeier, R A
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 10-07-1979
• Subjects: Chymotrypsin; Cyanogen Bromide; Erythrocyte Membrane - analysis; Erythrocytes - analysis; Ethylmaleimide; Humans; Membrane Proteins - blood; Molecular Weight; Peptide Fragments - analysis; Protein Binding; Sulfhydryl Compounds - blood; Trypsin
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)50530-5

Human erythrocyte membranes contain a major transmembrane protein, known as Band 3, that is involved in anion transport. This
protein contains a total of five reactive sulfhydryl groups, which can be assigned to either of two classes on the basis of
their susceptibility to release from the membrane by trypsin. Two of the groups are located in the region COOH-terminal to
the extracellular chymotrypsin-sensitive site of the protein and remain with a membrane-bound 55,000-dalton fragment generated
by trypsin treatment. The three sulfhydryl groups NH2-terminal to the extracellular chymotrypsin site are released from the
cytoplasmic surface of the membrane by trypsin. All three groups are present in a 20,000-dalton tryptic fragment of Band 3.
Two of these groups are located very close to the sites of trypsin cleavage that generate the 20,000-dalton fragment. The
third reactve group is probably located about 15,000-daltons from the most NH2-terminal sulfhydryl group. Two other well defined
fragments of the protein do not contain reactive sulfhydryl groups. They are a 23,000-dalton fragment derived from the NH2-terminal
end that is also released by trypsin from the cytoplasmic surface of the membrane and a 19,000-dalton membrane-bound region
of the protein that is produced by treatment with chymotrypsin in ghosts. The 20,000-dalton tryptic fragment may, therefore,
constitute a sulfhydryl-containing domain of the Band 3 protein.