K. Adachi et al., POLYMERIZATION OF RECOMBINANT HB S-KEMPSEY (DEOXY-R STATE) AND HB S-KANSAS (OXY-T STATE), The Journal of biological chemistry, 270(45), 1995, pp. 26857-26862
In order to investigate the role of the R (relaxed) to T (tense) struc
tural transition in facilitating polymerization of deoxy-Hb S, we have
engineered and expressed two Hb S variants which destabilize either T
state (Hb S-Kempsey, alpha(2) beta(2)(Val-6, Asn-99)). R State struct
ures (Hb S-Kansas, alpha(2) beta(2)(Val-6, Thr-102)), Polymerization o
f deoxy-Hb S-Kempsey, which shows high oxygen affinity and increased d
imer dissociation, required about 2- and Ci fold higher hemoglobin con
centrations than deoxy-fm S for polymerization in low and high phospha
te concentrations, and its kinetic pattern of polymerization was bipha
sic, In contrast, oxy- or CO Hb S-Kansas, which shows low oxygen affin
ity and increased dimer dissociation, polymerized at a slightly higher
critical concentration than that required for polymerization of deoxy
-Hb S in both low and high phosphate buffers, Polymerization of oxy- a
nd CO Kb S Kansas was linear and showed no delay time, which is simila
r to oversaturated oxy- or CO Hb S, These results suggest that nuclei
formation, which occurs during the delay time prior to deoxy-Hb S poly
merization, does not occur in T state oxy-Hb S-Kansas, even though the
critical concentration for polymerization of T state oxy-Hb S-Kansas
is similar to that of T state deoxy Hb S.