No abstract

The crystal structure of the tandem SH2 domains of human ZAP-70 in complex with a peptide derived from the zeta-subunit of the T-cell receptor reveals an unanticipated interaction between the two domains. A coiled coil of alpha-helices connects the two SH2 domains, producing an interface that constitutes one of the two critical phosphotyrosine binding sites. These and other unique features provide the molecular basis for highly selective association of ZAP-70 with the T-cell receptor.

The structure of a crystal complex of the chemically synthesized protease of human immunodeficiency virus 1 with a heptapeptide-derived inhibitor bound in the active site has been determined. The sequence of the inhibitor JG-365 is Ac-Ser-Leu-Asn-Phe-#[CH(OH)CH2N]-Pro-Ile-ValOMe; the K; is 0.24 nM. The hydroxyethylamine moiety, in place of the normal scissile bond of the substrate, is believed to mimic a tetrahedral reaction intermediate. The structure of the complex has been rermed to an R factor of 0.146 at 2.4A resolution by using restrained least squares with rms deviations in bond lengths of 0.02 A and bond angles of 4'. The bound inhibitor diastereomer has the S configuration at the hydroxyethylamine chiral carbon, and the hydroxyl group is positioned between the active site aspartate carboxyl groups within hydrogen bonding distance. Comparison of this structure with a reduced peptide bond inhibitor-protease complex indicates that these contacts confer the exceptional binding strength of JG-365.Reverse transcriptase, integrase, and protease are the three virally encoded enzymes necessary for replication of human immunodeficiency virus 1 (HIV-1), so each is a potential target for drug design. Rational design of drugs directed against AIDS would be greatly facilitated by knowledge of the three-dimensional structures of the target molecules, yet the protease is the only one of these enzymes for which the structure of the native form (1-3) or of an inhibitor complex (4) is known. The protease is a member of the wellcharacterized family of aspartic proteases, which also includes mammalian enzymes such as renin, pepsin, and chymosin. Whereas cell-encoded aspartic proteases are monomers with distinct amino and carboxyl domains, the retroviral proteases are dimers of identical subunits that are analogous to these domains (5). The function of the HIV-1 protease is to cleave the translated viral gag-pol polyprotein into discrete components. Without protease activity, the viral particle remains noninfective (6, 7) and this property makes the protease an attractive candidate for therapeutic drug design against AIDS (8)(9)(10)(11)(12)(13)(14).Inhibitors -of aspartic proteases have been developed as potential pharmaceutical agents for modulating the biological processes catalyzed by this class of enzymes (15,16 Herein we report the structure of a synthetic HIV-1 protease complexed with an HEA inhibitor, JG-365, and compare it with a complex structure in which the reduced peptide bond inhibitor MVT-101 was 3000 times less potent (4). The results substantiate a previously proposed mechanism of action for this class of enzymes (23) protease (where Aba is L-a-amino-n-butyric acid) was chemically synthesized as previously described (24,25). The sequence used was that of the SF2 isolate with cysteines replaced by L-a-amino-n-butyric acid (2). The inhibitor JG-365 was synthesized as described (22) The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby...

The Ras/Raf/MEK/ERK signal transduction, an oncogenic pathway implicated in a variety of human cancers, is a key target in anticancer drug design. A novel series of pyrimidylpyrrole ERK inhibitors has been identified. Discovery of a conformational change for lead compound 2, when bound to ERK2 relative to antitarget GSK3, enabled structure-guided selectivity optimization, which led to the discovery of 11e, a potent, selective, and orally bioavailable inhibitor of ERK.