Characterization of calpain I-binding proteins in human erythrocyte plasma membrane.
The calpain-binding components on the plasma membrane were characterized using calpain I. 125I-labeled calpain was bound to inside-out membrane vesicles from human erythrocyte in a Ca2(+)-dependent manner, but not to right-side-out membrane vesicles. The maximum binding was observed at more than 5 microM Ca2+. The binding amount of calpain to the inside-out membrane vesicles was decreased when the vesicles were pretreated with 100 micrograms/ml of trypsin, chymotrypsin, elastase, or pronase P for 30 min at 37 degrees C, although the binding to the vesicles pretreated with 200 micrograms/ml of phospholipase A2 or C was not affected. Calpain-binding proteins in the membrane were analyzed by using a modified immunoblotting for calpain. Immunostained bands of 240, 220, 89, 72, 52, and 36 kDa were detected as the calpain-binding proteins in the native membrane. All of these bands had disappeared in trypsin-treated membrane. The disappearance of bands was dose-dependent with respect to trypsin and paralleled the reduction of binding amount of calpain to the trypsinized membrane. In calpain-treated membrane, the 240 and 36 kDa bands were retained in the blotting, though the other bands disappeared dose-dependently with respect to calpain. These results suggested that the significant component in the inner surface of plasma membrane for binding of calpain was proteinaceous and the calpain-binding proteins could be classified into two species, i.e. substrates of calpain (220, 89, 72, and 52 kDa protein) and non-substrates (240 and 36 kDa protein).
Department of Clinical Biochemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Kanagawa.
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M
Kuboki
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H
Ishii
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M
Kazama
D002154:Calpain / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D004910:Erythrocyte Membrane / Q000201:enzymology*; D006801:Humans; D014357:Trypsin
D002352:Carrier Proteins; D014357:Trypsin; D002154:Calpain