PROTEIN 7.2B OF HUMAN ERYTHROCYTE-MEMBRANES BINDS TO CALPROMOTIN

Calpromotin is a soluble cytoplasmic protein of human red blood cells which is involved in the activation of the charybdotoxin-sensitive cal cium-dependent potassium channel. This activation is associated with i ncreased binding of calpromotin to the red cell membrane. To elucidate this mechanism we tested different fractions of red cell membrane pro teins to bind to a calpromotin affinity column, Proteins, which bound specifically to the column, were eluted and identified by SDS polyacry lamide gel electrophoresis, This procedure demonstrated that spectrin and actin, from a low salt extraction of the membrane, bound weakly to the column and a portion of this could be attributed to non-specific binding, Glyceraldehyde-3-phosphate dehydrogenase (band 6) and a 40K m olecular weight band, from a high salt extraction of the membrane, bou nd strongly to the affinity column, Several minor integral membrane pr oteins, obtained by Triton X-100 treatment of the membrane, bound spec ifically to the calpromotin affinity column, The molecular weight of t hese proteins ranged from 95k to 23K. We further demonstrated that the 31.5K band from this fraction is protein 7.2b (stomatin) by staining with a monoclonal antibody, Protein 7.2b is believed to have a role in regulating monovalent cation transport through the erythrocyte membra ne. (C) 1997 Academic Press.