AJP - Cell Physiology, Vol 234, Issue 1 36-C40, Copyright © 1978 by American Physiological Society
Binding of 2,3-diphosphoglycerate by spectrin and its effect on oxygen affinity of hemoglobin
N. Shaklai, L. Benitez and H. M. Ranney
The relationships between spectrin, a structural protein of the red blood
cell (RBC) membrane facing the cytoplasm, and hemoglobin were studied. The
oxygen-binding properties of stripped hemoglobin were not altered by the
presence of spectrin, but the interaction of hemoglobin with organic
phosphates was reduced by the addition of spectrin. The presence of the
enzyme glyceraldehyde 3-phosphate dehydrogenase (G3PD), another component
of the RBC membrane used as a control, did not change the oxygen affinity
of either stripped hemoglobin or of hemoglobin solutions containing
phosphates. Binding studies using the gel filtration method at pH 7.3
indicated reversible binding of 2,3-diphosphoglycerate to spectrin. A unit
of 220,000 daltons was calculated to have seven binding sites and a binding
constant of 1.2 X 10(4) M-1. A mechanism is proposed in which spectrin may
facilitate oxygen transport for hemoglobin molecules reaching the membrane.
