Molecular cloning and chemical synthesis of a region of platelet glycoprotein IIb involved in adhesive function

J. C. Loftus, E. F. Plow, A. L. Frelinger, S. E. D'Souza, D. Dixon, J. Lacy, J. Sorge, M. H. Ginsberg

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Abstract

Membrane glycoprotein (GP) IIb-IIIa is a component of a platelet adhesive protein receptor. A region of the heavy chain of GPIIb, defined by the monoclonal antibody PMI-1, is involved in adhesion receptor function. We have localized and chemically synthesized this region of GPIIb. A cDNA clone that directs the synthesis of a fusion protein reactive with the PMI-1 antibody was isolated from a phage λgt11 expression library constructed with mRNA from an erythroleukemia (HEL) cell line. The deduced amino acid sequence of this clone indicates that it spans the light-heavy chain junction of GPIIb and contains a portion of the carboxyl terminus of the heavy chain and the amino terminus of the light chain. The PMI-1 epitope was found to be contained within a 9-kDa staphylococcal V8 protease fragment of GPIIb, and such a fragment was predicted within the putative heavy-chain sequence. A computerized antigen prediction program identified a single sequence with a high probability of containing a continuous epitope. A synthetic 17-residue peptide containing this sequence binds PMI-1 and inhibits PMI-1 binding to GPIIb-IIIa. The peptide-antibody complex has an approximate K(d) of 1.2 μM, which compares to a K(d) of 0.95 μM for PMI-1 binding to GPIIb. The region containing the PMI-1 epitope shows no similarity to corresponding regions of two other adhesion receptors, indicating that this portion of GPIIb may function in activities unique to the platelet receptor.

Original languageEnglish (US)
Pages (from-to)7114-7118
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume84
Issue number20
DOIs
StatePublished - Jan 1 1987

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