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  • Title: Molecular recognition between serine proteases and new bioactive microproteins with a knotted structure.
    Author: Le Nguyen D, Heitz A, Chiche L, Castro B, Boigegrain RA, Favel A, Coletti-Previero MA.
    Journal: Biochimie; 1990; 72(6-7):431-5. PubMed ID: 2124146.
    Abstract:
    Microproteins with proteinase inhibitory activity, 28 to 30 amino acids long, with 3 disulfide bridges have been isolated from Ecballium elaterium seeds. A peptide (EETI II) was isolated and behaved as a powerful trypsin inhibitor (Kd = 10(-11) to 10(-12) M). It was sequenced, chemically synthesized and the 3-D structure determined by 2-D 1H NMR. The information gained in the process enabled us to synthesize modified derivatives with inhibitory activity towards pancreatic elastase, chymotrypsin and human leucocyte elastase (Kd = 10(-7) to 10(-9) respectively). The most striking characteristic that appeared during the synthetic approach was the unfailing ability of the 28 amino acid peptides to refold and correctly close the 3 disulfide bridges, giving in each case an active compound. These disulfide bridges are assembled in a particular knotted structure, shared by few other bioactive peptides and called the 'knottin' structure. Molecular modeling of the peptide and a comparison with the other active molecules with similar topology allowed the synthesis of a chimaeric peptide, bearing 1 active site against a seryl-protease (trypsin), and 1 against a metallo-protease (carboxypeptidase A). The bis-headed peptide was able to inhibit both enzymes separately and concomitantly.
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