Open AccessOrnatins: potent glycoprotein IIb‐IIIa antagonists and platelet aggregation inhibitors from the leech Placobdella ornata
Author(s) -
MAZUR Paul,
HENZEL William J.,
SEYMOUR Jana L.,
LAZARUS Robert A.
Publication year - 1991
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1991.tb16472.x
Subject(s) - leech , gene isoform , cysteine , biology , peptide sequence , biochemistry , microbiology and biotechnology , affinity chromatography , stereochemistry , chemistry , enzyme , gene , world wide web , computer science
The purification and characterization of six isoforms of ornatin, potent glycoprotein IIb‐IIIa (GP IIb‐IIIa) antagonists and platelet aggregation inhibitors are described. These isoforms were purified from whole leech homogenates of the leech Placobdella ornata , a North American leech commonly known as the turtle leech, by trichloroacetic acid precipitation, Sephadex G‐50 size exclusion chromatography, GP IIb‐IIIa affinity chromatography, and C 18 reverse‐phase HPLC. Each of the five completely sequenced isoforms, which range from 41 to 52 residues in lenght, contains the Arg‐Gly‐Asp (RGD) sequence, a common recognition sequence in adhesion proteins, as well as 6 cysteine residues; the positions of both of these features are conserved in the primary sequences. The amino acid sequences of ornatin isoforms B, C, D, and E are highly conserved, whereas ornatin A2 and A3 are less similar and lack 9 residues at the N‐terminus. The ornatins are approximately 40% identical with decorsin, a GP IIb‐IIIa antagonist isolated from the leech Macrobdella decora [Seymour, J. L., Henzel, W. J., Nevins, B., Stults, J. T. & Lazarus, R. A. (1990) J. Biol. Chem. 265 , 10143–10147]; furthermore, the RGD sequence and 5 out of 6 cysteine residues are maintained in the same relative positions in both decorsin and ornatin. The ornatin isoforms do not exhibit significant similarity to any members of the snake‐venomderived family of GP IIb‐IIIa antagonists [Dennis, M. S., Henzel, W. J., Pitti, R. M., Lipari, M. T., Napier, M. A., Deisher, T. A., Bunting, S. & Lazarus, R. A. (1990) Proc. Natl Acad. Sci. USA 87 , 2471–2475] except in the RGD region of these proteins. The ornatin isoforms inhibit the binding of GP IIb‐IIIa to immobilized fibrinogen with IC 50 values ranging over 2.9–5.3 nM; ornatin isoforms A2, C, and E inhibit ADP‐induced human platelet aggregation with IC 50 values of about 130, 280, and 440 nM, respectively.