Characterization of apocytochrome C binding to human erythrocytes.
The binding of 125I-labeled apocytochrome c to human erythrocytes was determined for free apocytochrome c concentrations at 10(-10)-10(-6) M. At about 2 x 10(-9) M, maximum cell association of apocytochrome c occurs at 50 mM NaCl and at 22 degrees C. Intact erythrocytes at 22 degrees C have three classes of apocytochrome c binding sites: one high-affinity noncooperative site (n1 = 728 per cell, Kd1 = 1.5 x 10(-9) M) and two positively cooperative sites (n2 = 3.7 x 10(4) per cell, Kd2 = 1.2 x 10(-7) M, alpha 2 = 2.0, and n3 = 2.5 x 10(5) per cell, Kd3 = 7.1 x 10(-7) M, alpha 3 = 12). Erythrocytes at 37 degrees C, and erythrocyte ghosts at 22 degrees C, also have three classes of apocytochrome c binding sites, and most sites are positively cooperative.
Krishnan
G
G
Department of Pharmacy, University of California, San Francisco 94143-0446.
MacGregor
R D
RD
Shohet
S B
SB
Hunt
C A
CA
D001059:Apoproteins / Q000378:metabolism*; D001665:Binding Sites; D003574:Cytochrome c Group / Q000378:metabolism*; D045304:Cytochromes c; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007457:Iodine Radioisotopes
D001059:Apoproteins; D003574:Cytochrome c Group; D007457:Iodine Radioisotopes; D045304:Cytochromes c