A series of peptide derivatives based on the transition-state mimetic concept has been designed that inhibit the proteinase from the human immunodeficiency virus (HIV). The more active compounds inhibit both HIV-1 and HIV-2 proteinases in the nanomolar range with little effect at 10 micromolar against the structurally related human aspartic proteinases. Proteolytic cleavage of the HIV-1 gag polyprotein (p55) to the viral structural protein p24 was inhibited in chronically infected CEM cells. Antiviral activity was observed in the nanomolar range (with one compound active below 10 nanomolar) in three different cell systems, as assessed by p24 antigen and syncytium formation. Cytotoxicity was not detected at 10 and 5 micromolar in C8166 and JM cells, respectively, indicating a high therapeutic index for this new class of HIV proteinase inhibitors.

No abstract

The influenza virus RNA-dependent RNA polymerase protein complex contains an associated RNA endonuclease activity, which cleaves host mRNA precursors in the cell nucleus at defined positions 9-15 nucleotides downstream of the cap structure. This reaction provides capped oligoribonucleotides, which function as primers for the initiation of viral mRNA synthesis. The endonuclease reaction is dependent on the presence of divalent metal ions. We have used a number of divalent and trivalent metal ions alone and in combination to probe the mechanism of RNA cleavage by the influenza virus endonuclease. Virus-specific cleavage was observed with various metal ions, and maximum cleavage activity was obtained with 100 microM Mn2+ or 100 microM Co2+. This activity was about 2-fold higher than that observed with Mg2+ at the optimal concentration of 1 mM. Activity dependence on metal ion concentration was cooperative with Hill coefficients close to or larger than 2. Synergistic activation of cleavage activity was observed with combinations of different metal ions at varying concentrations. These results support a two-metal ion mechanism of RNA cleavage for the influenza virus cap-dependent endonuclease. The findings are also consistent with a structural model of the polymerase, in which the specific endonuclease active site is spatially separated from the nucleotidyl transferase active site of the polymerase module.

The title compound, CI7H28N407, is a synthetic crystalline cyclic tetrapeptide containing alternate 0c-amino peptide groups and fl-amino peptide groups similar to the naturally occurring depsipeptide serratamolide. The tetrapeptide represents a preliminary step in the proposed synthesis of a cylindrical polypeptide. The 14-membered 'ring' consists of four planar segments with each segment in the trans conformation. The corner atoms are C'(1), Ca(2), C~(3) and Ca(4). Two carbonyl oxygens are directed above the average plane of the ring and the other two below. If the side chains are disregarded, two of the peptide groups are related to the other two by an approximate center of symmetry. In the crystal the molecules are stacked over each other by translation in the a direction. Between each pair of molecules in the stack there are two NH. • • O bonds at 2-86 A. The remaining two NH moieties do not participate in hydrogen bonding. The space group is P21 with a=5.624 (4), b= 10.298 (7), c= 17.859 (13) A, and fl= 99"07 (5) °. The structure was solved by the symbolic addition procedure.

N-terminal analysis of aggrecan fragments lost from bovine nasal cartilage cultured in the presence of recombinant human interleukin 1alpha revealed a predominant ARGSVIL sequence with an additional ADLEX sequence. Production of the ARGSVIL-containing fragments has been attributed to the action of a putative proteinase, aggrecanase. The minor sequence (ADLEX) corresponds to a new reported cleavage product; comparison of this sequence with the available partial sequence of bovine aggrecan indicates that this is the product of a cleavage occurring towards the C-terminus of the protein. Matrix metalloproteinase (MMP) inhibitors inhibited aggrecan loss from bovine nasal explants incubated in the presence of recombinant human interleukin 1alpha. A strong correlation between inhibition of aggrecan metabolism and inhibition of stromelysin 1 (MMP 3) (r=0.93) suggests a role for stromelysin or a stromelysin-like enzyme in cartilage aggrecan metabolism. However, the compounds were approx. 1/1000 as potent in inhibiting aggrecan loss from the cartilage explants as they were in inhibiting stromelysin. There was little or no correlation between inhibition of aggrecan metabolism and inhibition of gelatinase B (MMP 9) or inhibition of collagenase 1 (MMP 1). Studies with collagenase inhibitors with a range of potencies showed a correlation between inhibition of collagenase activity and inhibition of collagen degradation in the cartilage explant assay. This indicates that in interleukin 1alpha-driven bovine nasal cartilage destruction, stromelysin (or a closely related enzyme) is involved in aggrecan metabolism, whereas collagenase is principally responsible for collagen degradation.