The N-proximal region of cowpea chlorotic mottle virus (CCMV) capsid protein (CP) contains an argininerich RNA binding motif (ARM) that is also found in the CPs of other members of Bromoviridae and in other RNA binding proteins such as the Tat and Rev proteins of human immunodeficiency virus. To assess the critical role played by this motif during encapsidation, a variant of CCMV RNA3 (C3) precisely lacking the ARM region (C3/⌬919) of its CP gene was constructed. The biology and the competence of the matured CP derived in vivo from C3/⌬919 to assemble and package progeny RNA was examined in whole plants. Image analysis and computer-assisted three-dimensional reconstruction of wild-type and mutant virions revealed that the CP subunits bearing the engineered deletion assembled into polymorphic virions with altered surface topology. Northern blot analysis of virion RNA from mutant progeny demonstrated that the engineered mutation down-regulated packaging of all four viral RNAs; however, the packaging effect was more pronounced on genomic RNA1 and RNA2 than genomic RNA3 and its CP mRNA. In vitro assembly assays with mutant CP subunits and RNA transcripts demonstrated that the mutant CP is inherently not defective in packaging genomic RNA1 (53%) and RNA2 (54%), but their incorporation into virions was competitively inhibited by the presence of other viral RNAs. Northern blot analysis of RNA encapsidation in vivo of two distinct bromovirus RNA3 chimeras, constructed by exchanging CPs having the ⌬919 deletion, demonstrated that the role of the conserved N-terminal ARM in recognizing and packaging specific RNA is distinct for each virus.The first 25 N-terminal amino acids of the capsid proteins (CPs) of the members of genera Bromovirus, brome mosaic virus (BMV) and cowpea chlorotic mottle virus (CCMVs), have a highly conserved arginine-rich motif (ARM) (26,32). In addition to the bromoviruses, this ARM, which recognizes specific regions in RNA, is also found in other plant virus genera, such as Cucumovirus, Sobemovirus, and Tombusvirus, and in human immunodeficiency virus Tat and Rev proteins, bacterial antiterminators, and ribosomal proteins of nonplant viruses (4,26,32).The genomes of BMV and CCMV are divided among three genomic RNAs. Viral RNA replication is dependent on efficient interaction between two nonstructural proteins, 1a and 2a, encoded by monocistronic RNA1 and RNA2, respectively (16). The two gene products encoded by the dicistronic RNA3 are dispensable for viral replication but are required for infection in plants (10,20,25,26,30). The genomic RNA3 encodes a nonstructural protein of 32 kDa, designated the movement protein (MP) (20,25,26), and a 19-kDa CP that is synthesized from a subgenomic RNA4 (CP mRNA) derived from progeny minus-strand RNA3 by internal initiation (19). The three genomic RNAs and a single subgenomic RNA4 are packaged into three physically and morphologically indistinguishable icosahedral virions (24). These virions having Tϭ3 symmetry are assembled from 180 identical subunits of a sin...

Retroviral envelope glycoproteins undergo proteolytic processing by cellular subtilisin-like proprotein convertases at a polybasic amino-acid site in order to produce the two functional subunits, SU and TM. Most previous studies have indicated that envelope-protein cleavage is required for rendering the protein competent for promoting membrane fusion and for virus infectivity. We have investigated the role of proteolytic processing of the Moloney murine leukemia virus envelope-protein through site-directed mutagenesis of the residues near the SU-TM cleavage site and have established that uncleaved glycoprotein is unable either to be incorporated into virus particles efficiently or to induce membrane fusion. Additionally, the results suggest that cleavage of the envelope protein plays an important role in intracellular trafficking of protein via the cellular secretory pathway. Based on our results it was concluded that a positively charged residue located at either P2 or P4 along with the arginine at P1 is essential for cleavage.

Background: Ageing is a universal phenomenon for all the living subjects. Various theories exist for the process of ageing, but the highly accepted theory is "Free Radical Theory of Ageing" conceived by Harman. According to this theory there is some imbalance between production and scavenging mechanisms of free radicals. The free radicals produce damage over the lifetime which is critical in determining the life span of individual. In context of this theory the present study was conceived. Objective: To investigate the correlation of free radicals and ageing process in human individuals. Materials and Methods: Adult volunteers with the age of 21 to 80 yrs were divided into three groups of 21-40 yrs, 41-60 yrs and 61-80 yrs. In each group there were 30 individuals. The serum levels of Glutathione reductase (GSSG-reductase) and Total antioxidant status (TAS) were measured in all the individuals. The data was subjected to ANOVA. Then student's unpaired T-test was used for evaluation and the values of P < 0.05 were considered statistically significant. The data was also analyzed for correlation coefficient (r). Results: The levels of GSSG-reductase and TAS were significantly lower in 61-80 yrs age group. There was negative correlation between ageing versus GSSG-reductase as well as TAS. Conclusion: Oxidative stress is generated during various stages of life. The gradual but steady fall of the antioxidant GSSG-reductase and falling level of TAS provide reasonable indication of weakness in antioxidant shield for the individuals. It is concluded that there is correlation between generation of free radicals and ageing process.

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