Hemoglobin Saint Mandé [beta 102 (G4) Asn----Tyr]. Functional studies and structural modeling reveal an altered T state.
Oxygen equilibrium studies of purified hemoglobin Saint Mandé (Hb SM) [beta 102 (G4) Asn----Tyr] reveal a decreased oxygen affinity and cooperativity but to a lesser extent than found for Hb Kansas (beta 102 Thr). The low affinity of Hb SM depends on environmental conditions: eliminating chloride or raising the pH greatly elevated the ratio of p50 of Hb SM to that of Hb A. The alkaline Bohr effect is reduced by about 40%. The effects of anions (chloride, organophosphates) binding to deoxy Hb SM are also reduced. These data indicate that the functional properties of Hb SM are intermediary between Hb A and Hb Kansas. In addition, molecular graphics modeling of Hb SM in the oxy and deoxy structures indicate the possibility of a new hydrogen bond in the T state between beta(1)102 Tyr and alpha(2)42 Tyr. Stabilisation of the T state in this manner is a plausible explanation for several of the effects observed.
Poyart
C
C
Institut National de la Santé et de la Recherche Médicale, Faculté de Médecine Paris-Sud, France.
Schaad
O
O
Kister
J
J
Galacteros
F
F
Edelstein
S J
SJ
Blouquit
Y
Y
Arous
N
N
D001216:Asparagine / Q000235:genetics; D006455:Hemoglobins, Abnormal / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D014443:Tyrosine / Q000235:genetics
D006455:Hemoglobins, Abnormal; D014443:Tyrosine; D001216:Asparagine; C030556:hemoglobin Saint Mande; D010100:Oxygen