PSEUDOPEPTIDE TASP INHIBITORS OF HIV ENTRY BIND SPECIFICALLY TO A 95-KDA CELL-SURFACE PROTEIN

The template assembled synthetic peptide constructs (TASP), pentavalen tly presenting the tripeptide RPR or RPK are potent and specific inhib itors of human immunodeficiency virus (HIV) infection by preventing vi ral entry into permissive cells. Here the 5[K Psi(CH2N)PR]-TASP constr uct, Psi(CH2N) for reduced peptide bond, was used in studies to demons trate its specific binding to a 95-kDa cell surface protein ligand, Co mpared to its nonreduced 5[KPR]-TASP counterpart, the pseudopeptide 5[ K Psi(CH2N)PR]-TASP manifested higher affinity to bind to its cell sur face ligand, increased activity to inhibit HIV infection, and resistan ce to degradation when incubated in serum from an HIV-1 seropositive i ndividual, In ligand blotting experiments, the biotin-labeled 5[K Psi( CH2N)PR]-TASP identified a single 95-kDa protein in crude cell extract s. This 95-kDa protein (p95) is expressed on the cell surface since su rface iodination of cells resulted in its labeling, and moreover, foll owing incubation of cells with the biotin-labeled 5[K Psi(CH2N)PR]-TAS P, the p95 TASP complex was recovered by affinity chromatography using avidin;agarose, All anti-HIV TASP constructs but not their control de rivatives affected the binding of biotin-labeled 5[K Psi(CH2N)PR]-TASP to p95, thus emphasizing the specific nature of this binding, Since 5 [K Psi(CH2N)PR]-TASP does not interact with HIV-envelope glycoproteins , our results suggest that TASP inhibitors mediate directly or indirec tly a block in HIV-mediated membrane fusion process by binding to the cell surface expressed p95.