Effect of heat on the circular dichroism of spectrin in hereditary pyropoikilocytosis.

Hereditary pyropikilocytosis is a hemolytic anemia in which the erythrocytes show increased sensitivity to heat-induced fragmentation. Circular dichroism measurements were employed to study the effect of heat on the secondary structure of pyropoikilocyte membrane proteins. The magnitude of the ellipticity at 222 nm over the temperature range from 25 degrees to 70 degrees C was determined for erythrocyte ghosts, spectrin, and ghost residue after extraction. In pyropoikilocyte ghosts, protein denaturation began at a lower temperature and the midpoint of the structural transition was displaced from 49 degrees C (the value for normal ghosts) to 44 degrees C. This thermal transition was present in spectrin, but not in the ghost residue after extraction. We conclude that an abnormality in the spectrin molecule alters the physical and morphologic properties of the erythrocyte membrane in pyropoikilocytosis.