The interaction between the highly basic and cytotoxic eosinophil cationic protein (ECP) and human plasma proteins is described. The major plasma protein responsible for complex-formation with ECP was shown to be the ‘fast’ form of alpha 2-macroglobulin (alpha 2M). Large amounts of complexes were observed in a serum obtained from a patient with hypereosinophilic syndrome. The amount of complexes that could be generated in vitro in normal fresh serum was rather low and was even less in fresh citrated plasma. Complex-formation between the non-proteolytic ECP and alpha 2M was augmented in the presence of methylamine. Binding of ECP to alpha 2M was also induced by the proteinases cathepsin G and thrombin, and the binding was competitive with cathepsin G. Methylamine and the proteinases seem to share a common mechanism in inducing binding of ECP. The nature of the ECP-alpha 2M interaction is non-covalent, but withstands high salt concentrations. The interaction with alpha 2M may reflect a mechanism by which the organism protects itself against the deleterious effects of the highly cytotoxic protein ECP.
Research Article|August 01 1987
Interaction and complex-formation between the eosinophil cationic protein and α2-macroglobulin
C G Peterson;
Biochem J (1987) 245 (3): 781-787.
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C G Peterson, P Venge; Interaction and complex-formation between the eosinophil cationic protein and α2-macroglobulin. Biochem J 1 August 1987; 245 (3): 781–787. doi: https://doi.org/10.1042/bj2450781
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