RESUMO
The disruption of the viral coat of human immunodeficiency virus by Triton X-100, a nonionic detergent, is a time-dependent process which requires incubation times of 30 min or longer. Conditions for the production of a noninfectious sample from a viral pellet that can be used to measure reverse transcriptase activity were determined.
Assuntos
Transcriptase Reversa do HIV/metabolismo , HIV-1/fisiologia , Virologia/métodos , Linhagem Celular , Glicerol , HIV-1/enzimologia , Humanos , Octoxinol , Segurança , Vírion/enzimologia , Vírion/fisiologiaRESUMO
Two isozymes of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) of the apicomplexan protozoan Toxoplasma gondii are encoded by the single HGPRT gene as a result of differential splicing. Western blotting of total T. gondii protein shows that both isozymes I and II, which differ by 49 amino acids, are expressed. Both form enzymatically active homotetramers when overexpressed in Escherichia coli. The specific activity of HGPRT-I is five times that of HGPRT-II. When both isozymes are co-expressed in E. coli, HGPRT-I.HGPRT-II heterotetramers form. The predominant heterotetramer has enzymatic activity similar to HGPRT-II, and gel filtration chromatography demonstrates that its size is intermediate between the sizes of HGPRT-I and HGPRT-II. Mass spectrometric analysis of cross-linked homo- and heterotetramers reveals species of distinct molecular mass for HGPRT-I, HGPRT-II, and HGPRT-I.HGPRT-II and suggests that the predominant heterotetramer consists of one HGPRT-I subunit and three HGPRT-II subunits. The implications of this finding are discussed.
Assuntos
Hipoxantina Fosforribosiltransferase/química , Isoenzimas/química , Toxoplasma/enzimologia , Animais , Biopolímeros , Western Blotting , Cromatografia em Gel , Escherichia coli/genética , Hipoxantina Fosforribosiltransferase/genética , Hipoxantina Fosforribosiltransferase/isolamento & purificação , Isoenzimas/genética , Isoenzimas/isolamento & purificação , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
The anti-HIV activities of two new polyanionic polymers (AM 242 and AM 612) were investigated in cell culture-based and biochemical antiviral assays. These compounds inhibited the reverse transcriptases from HIV-1 and HIV-2, using enzyme purified from virions and either a ribosomal RNA or gapped duplex DNA as the template. With the ribosomal RNA template, AM 242 and AM 612 had ID50 values of 1.1 and 0.10 micrograms/ml against the HIV-1 reverse transcriptase. In vitro cell based assays determined that both compounds significantly inhibited both the cytopathic effects associated with HIV-1 infection and the replication of virus in infected cells. AM 242 had an IC50 of approximately 1.0 micrograms/ml, while that of AM 612 was 0.19 micrograms/ml. These two active polyanionic polymers were effective in inhibiting the growth of a panel of HIV-1 isolates and were also active against HIV-2. Although the compounds were toxic at high concentration, they had antiviral activity over a wide range of nontoxic concentrations, yielding a high selectivity index. AM 612 was 100% protective for CEM cells from 320 ng/ml to 1 microgram/ml. Both compounds caused a significant increase in cellular proliferation as determined by the concentration-dependent increase in incorporation of radioactive precursors into cellular macromolecules.