Membrane protein interactions in sickle red blood cells: evidence of abnormal protein 3 function.
The pattern of membrane abnormalities in sickle red blood cells suggests that sickle hemoglobin damages membrane proteins. We have previously shown a functional defect in sickle ankyrin, poor spectrin-binding ability. Here we examine the other major binding interactions of sickle membrane proteins including spectrin self-association, binding of ankyrin and protein 4.1 to protein 3, and the formation of the spectrin-actin-protein 4.1 complex. We found that sickle spectrin was normal in self-association and ability to participate in the spectrin-actin-protein 4.1 complex. Sickle protein 4.1 bound normally to protein 3 and formed normal complexes with actin and spectrin, even when sickle spectrin was used. The only major abnormality we found was a reduced ability of sickle protein 3 to bind ankyrin. This functional defect could not be explained experimentally on the basis of cysteine modification or enhanced tyrosine phosphorylation. We conclude that damage of sickle membrane proteins is not a diffuse scattershot process, but is largely confined to regions near membrane-associated hemoglobin, the spectrin-binding domain of ankyrin and the ankyrin-binding domain of protein 3. The mechanism and consequences of this damage continues to be investigated.
Platt
O S
OS
Department of Pediatrics, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Falcone
J F
JF
D000755:Anemia, Sickle Cell / Q000097:blood*; D001457:Anion Exchange Protein 1, Erythrocyte / Q000302:isolation & purification / Q000378:metabolism*; D017487:Ankyrins / Q000302:isolation & purification / Q000378:metabolism; D003598:Cytoskeletal Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000097:blood* / Q000302:isolation & purification / Q000378:metabolism; D009479:Neuropeptides; D011485:Protein Binding; D012016:Reference Values; D013049:Spectrin / Q000302:isolation & purification / Q000378:metabolism
D001457:Anion Exchange Protein 1, Erythrocyte; D017487:Ankyrins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009479:Neuropeptides; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; D013049:Spectrin