Chrysoptin is a potent glycoprotein IIb/IIIa fibrinogen receptor antagonist present in salivary gland extracts of the deerfly.
Salivary gland lysates of the deerfly (genus Chrysops) contain chrysoptin, an inhibitor of ADP-induced platelet aggregation, which presumably assists the fly in obtaining a blood meal. Chrysoptin has now been isolated, and its cDNA has been cloned and expressed. Chrysoptin was purified to homogeneity using anion exchange and hydrophobic interaction chromatography and found to be a protein with a molecular mass of 65 kDa as determined by gel electrophoresis. N-terminal amino acid sequencing allowed for the synthesis of degenerate oligonucleotides that led to cloning, from salivary gland specific mRNA, of the cDNA encoding this platelet inhibitor. No RGD sites are present in the predicted sequence. A search of GenBank(TM) did not reveal significant sequence homology between chrysoptin and other proteins. The molecular mass predicted from the cDNA was 59 kDa. Predicted glycosylation and phosphorylation sites may account for this difference in molecular mass, as recombinant chrysoptin expressed in Sf21 cells had a molecular mass of 65 kDa, matching that of the natural protein. Chrysoptin functions by inhibiting the binding of fibrinogen to the fibrinogen/glycoprotein IIb/IIIa receptor on platelets with an IC(50) of 95 pmol. These results reveal that insect salivary glands are a source of fibrinogen receptor antagonists.
Reddy
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VB
Cutaneous Biology Research Center, Massachusetts General Hospital and Department of Dermatology, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
Kounga
K
K
Mariano
F
F
Lerner
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EA
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D004175:Diptera / Q000737:chemistry / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D005340:Fibrinogen / Q000037:antagonists & inhibitors / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D010974:Platelet Aggregation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors*; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D012469:Salivary Glands / Q000737:chemistry / Q000378:metabolism
D019476:Insect Proteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011506:Proteins; C410038:chrysoptin protein, Chrysops; D000244:Adenosine Diphosphate; D005340:Fibrinogen