A new monoclonal antibody to an age sensitive band 3 transmembrane segment

The appearance of band 3 structural modifications related to aging could be evidenced by means of monoclonal antibodies against senescence antigen. Hence in the attempt to provide an immunological marker of erythrocyte aging, we raised a monoclonal antibody against native band 3 (B6 MoAb), which seems to detect differences in the band 3 molecule from erythrocytes of different ages separated by density gradient. Densitometric evaluation of immunoblotting patterns indicates that the in vivo aging is associated with band 3 monomer degradation. The Percoll separated fractions show a significant increase of those proteolytic fragments that bind the B6 antibody. Finally, protease digestions of unsealed membrane ghosts have been performed to test the binding site of the B6 antibody on the band 3 molecule. The data show that the B6 antibody binds a 19 KDa chymotryptic-tryptic fragment which corresponds to a segment of the looped membrane domain whose steric structure appears to be sensitive to age.