Virions

Ara-A-5 -monophosphate [29984-33-6] (ara-AMP), C2QH24N OyP, is more water-soluble than ara-A, and therefore can be used in higher dosage during the first hours of treatment of viral infections. Ara-AMP has been shown to decrease virion-associated DNA polymerase concentrations in ground squirrels carrying ground squirrel hepatitis vims. The hypoxanthine derivative, ara-HxMP [54656-49-4] (24) is more water-soluble, appears to have a similar antiviral spectmm to ara-A, and is considerably less toxic (48). 

Reverse transcriptase (from avian or murine RNA tumour viruses) [9068-38-6] [EC 2.7.7.49]. Purified by solubilising the virus with non-ionic detergent. Lysed virions were adsorbed on DEAE-cellulose or DEAE-Sephadex columns and the enzyme eluted with a salt gradient, then chromatographed on a phosphocellulose column and enzyme activity eluted in a salt gradient. Purified from other viral proteins by affinity chromatography on a pyran-Sepharose column. [Verna Biochim Biophys Acta 473 1 7977 Smith Methods Enzymol 65 560 1980 see commercial catalogues for other transcriptases.]... 

The role of the viral neuraminidase, conversely, seems to be to facilitate the release of progeny virions from infected cells by cleaving sialic acid... 

The shell of all picomaviruses is built up from 60 copies each of four polypeptide chains, called VPl to VP4. These are translated from the viral RNA into a single polypeptide, which is posttranslationally processed by stepwise proteolysis involving viraily encoded enzymes. First, the polypeptide chain is cleaved into three proteins VPO (which is the precursor for VP2 and VP4), VPl and VP3. These proteins begin the assembly process. The last step of the processing cascade occurs during completion of the virion assembly the precursor protein VPO is cleaved into VP2 and VP4 by a mechanism that is probably autocatalytic but may also involve the viral RNA. VPl, VP2, and VP3 have molecular masses of around 30,000 daltons, whereas VP4 is small, being 7000 daltons, and is completely buried inside the virion. 

The asymmetric unit contains one copy each of the subunits VPl, VP2, VP3, and VP4. VP4 is buried inside the shell and does not reach the surface. The arrangement of VPl, VP2, and VP3 on the surface of the capsid is shown in Figure 16.12a. These three different polypeptide chains build up the virus shell in a way that is analogous to that of the three different conformations A, C, and B of the same polypeptide chain in tomato bushy stunt virus. The viral coat assembles from 12 compact aggregates, or pen tamers, which contain five of each of the coat proteins. The contours of the outward-facing surfaces of the subunits give to each pentamer the shape of a molecular mountain the VPl subunits, which correspond to the A subunits in T = 3 plant viruses, cluster at the peak of the mountain VP2 and VP3 alternate around the foot and VP4 provides the foundation. The amino termini of the five VP3 subunits of the pentamer intertwine around the fivefold axis in the interior of the virion to form a p stmcture that stabilizes the pentamer and in addition interacts with VP4. 

Choi, H.-K., et al. Structure of Sindbis virus core protein reveals a chymotrypsin-like serine proteinase and the organization of the virion. Nature 354 37-43, 1991. 

Smith, G.P. Filamentous fusion phage novel expression vectors that display cloned antigens on the virion surface. Science 228 1315-1317, 1985. 

In cell culture, it has been shown that one virion can produce infection. In the human host, because of acquired resistance and a variety of other factors, the one virion/one infection possibility does not exist. 

Vibrio (i) Curved, rod-shaped bacterial cell, (ii) Bacterium of the genus Vibrio. Virion Virus particle the virus nucleic acid surrounded by protein coat and in some cases other material. 

Cross-packaging is the packaging of viral genomes into the virion shell of other viruses. 

The development of AAV-based gene-therapy vectors is presently focused on the analysis of the properties of the different AAV serotypes, especially the host range of the virion shells of the different serotypes. By packaging... 

Ho DD, Neumann AU, Perelson AS, Chen W, Leonard JM, Markowitz M (1995) Rapid turnover of plasma virions and CD4 lymphocytes in HIV-1 infection. Nature 373 123-126... 

Gibson W (1996) Structure and assembly of the virion. Intervirology 39 389 00 Goldman ME, Nunberg JH, O Brien JA, Quintero JC, Schleif WA, Freund KF, Gaul SL, Saari WS, Wai IS, Hoffman JM et al. (1991) Pyridinone derivatives specific human immunodeficiency virus type 1 reverse transcriptase inhibitors with antiviral activity. Proc Natl Acad Sci USA... 

Zhou J, Yuan X, Dismuke D et al, (2004) Small-molecule inhibition of human immunodeficiency virus type 1 replication by specific targeting of the final step of virion maturation, J Virol 78 922-929... 

Fernie BF, Poli G, Fauci AS (1991) Alpha interferon suppresses virion but not soluble human immunodeficiency virus antigen production in chronically infected T-lymphocytic cells. J Virol 65 3968-3971... 

Infection is established Viral genes expressed Viral genome replicated Production of infectious virions blocked No protection from CPE No protection from CTL No selective advantage... 

Fig. 1 Antiviral genes inhibit virus replication at different stages of the viral life cycle. Early inhibitors prevent the establishment of the viral genome in the target cell (class I, e.g., entry inhibitors, RT inhibitors for HIV). Intermediate inhibitors prevent viral gene expression or amplification of the viral genome (class II, e.g., siRNAs, antisense RNAs). Late inhibitors prevent virion assembly or release, or inactivate the mature virions (class III, e.g., transdominant core proteins, capsid-targeted virion inactivation, CTVI). A list of antiviral genes in each class is found in Table 1...

Kobinger GP, Borsetti A, Nie Z, Mercier J, Daniel N, Gotthnger HG, Cohen A (1998) Virion-targeted viral inactivation of human immunodeficiency virus type 1 by using Vpr fusion proteins. J Virol 72 5441-5448... 

Kaushik N., Pandey V. N. PNA targeting the PBS and A-loop sequences of HIV-1 genome destabilizes packaged tRNA3(Lys) in the virions and inhibits HIV-1 replication. Virology 2002 ... 

Perelson AS, Neumann AU, Markowitz M, Leonard JM, Ho DD. HlV-1 dynamics in vivo virion clearance rate, infected cell life-span, and viral generation time. Science 1996 271 1582-6. 

Zheng J, Ghorpade A, Niemann D, Cotter RL, Thylin MR, Epstein L, Swartz JM, Shepard RB, Liu X, Nukuna A, Gendelman HE (1999a) Lymphotrofric virions affect chemokine receptor-mediated neural signaling and apoptosis implications for human immunodeficiency virus type 1-associated dementia. J Virol 73(10) 8256-8267... 

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