Effect of mutations in sequences adjacent to the deoxyHb binding site on cdb3 on Hb-O2 equilibrium. (A) Hb-oxygen dissociation curves were measured for Hb alone (a), Hb in the presence of wild type cdb3 (b), 6NNYQN10 (c), del(1-11) (d), thioredoxin-(1-55) (e), or del (29-52) (f). (B) Comparison of P50 values in the presence and absence of the above truncation mutants (error bars represent 1 SD).