Fr. Smith et Kc. Simmons, CYANOMET HUMAN HEMOGLOBIN CRYSTALLIZED UNDER PHYSIOLOGICAL CONDITIONSEXHIBITS THE Y-QUATERNARY STRUCTURE, Proteins, 18(3), 1994, pp. 295-300
Cyanomet human hemoglobin has been crystallized at a chloride ion conc
entration and pH similar to physioloscal conditions. Molecular replace
ment calculations definitively show that the hemoglobin subunits are a
rranged in the Y quaternary form recently discovered in carbon monoxy
hemoglobin Ypsilanti (beta 99 Asp-Tyr), and subsequently observed in c
arbon monoxy normal human hemoglobin crystallized at low ionic strengt
h and low pH. The structure has been refined at 2.09 Angstrom resoluti
on to an R-value of 0.232, and further refinement is currently underwa
y. Although the refinement is not yet complete, our results are the fi
rst indication that the Y structure may represent an important quatern
ary form of liganded hemoglobin under physiological buffer conditions.
These results suggest the need for a reexamination of structure-funct
ion correlations in the hemoglobin system. (C) 1994 Wiley-Liss, Inc.