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21.
An inhibitor of microRNA-122 reduces viral load in chimpanzees that are chronically infected with hepatitis C virus, suggesting
that such an approach might have therapeutic potential in humans. 相似文献
22.
Salmonella phage P22, which serves as an assembly paradigm for icosahedral double-stranded DNA viruses, packages its viral genome through a capsid channel (portal) comprising 12 copies of a 725-residue subunit. Secondary and tertiary structures of the portal subunit in monomeric and dodecameric states have been investigated by Raman spectroscopy using a His6-tagged recombinant protein that self-assembles in vitro [Moore, S. D., and Prevelige, P. E., Jr. (2001) J. Biol. Chem. 276, 6779-6788]. The portal protein exhibits Raman secondary structure markers typical of a highly alpha-helical subunit fold that is little perturbed by assembly. On the other hand, Raman markers of subunit side chains change dramatically with assembly, an indication of extensive changes in side chain environments. The cysteinyl Raman signature of the portal consists of a complex pattern of sulfhydryl stretching bands, revealing diverse hydrogen-bonding states for the four S-H groups per subunit (Cys 153, Cys 173, Cys 283, and Cys 516). Upon assembly, the population of strongly hydrogen-bonded S-H groups decreases, while the population of weakly hydrogen-bonded S-H groups increases, implying that specific intrasubunit S-H.X hydrogen bonds must be weakened to effect dodecamer assembly and that the molecular mechanism involves reorganization of subunit domains without appreciable changes in domain conformations. Comparison with other viral protein assemblies suggests an assembly process not requiring metastable intermediates. The recently published X-ray structure of the phi29 portal [Simpson, A. A., et al. (2000) Nature 408, 745-750] shows that residues 125-225 lining the channel surface form alpha-helical modules spaced by short beta-strands and turns; a surprisingly close secondary structure homology is predicted for residues 240-350 of the P22 portal, despite no apparent sequence homology. This motif is proposed as an evolutionarily conserved domain involved in DNA translocation. 相似文献
23.
Structural studies of acetylated and control inner core histones 总被引:4,自引:0,他引:4
24.
25.
Monroe EB Kang S Kyere SK Li R Prevelige PE 《Structure (London, England : 1993)》2010,18(11):1483-1491
Following budding, HIV-1 virions undergo a maturation process where the Gag polyprotein in the immature virus is cleaved by the viral protease and rearranges to form the mature infectious virion. Despite the wealth of structures of isolated capsid domains and an in?vitro-assembled mature lattice, models of the immature lattice do not provide an unambiguous model of capsid-molecule orientation and no structural information is available for the capsid maturation pathway. Here we have applied hydrogen/deuterium exchange mass spectrometry to immature, mature, and mutant Gag particles (CA5) blocked at the final Gag cleavage event to examine the molecular basis of capsid assembly and maturation. Capsid packing arrangements were very similar for all virions, whereas immature and CA5 virions contained an additional intermolecular interaction at the hexameric, 3-fold axis. Additionally, the N-terminal β-hairpin was observed to form as a result of capsid-SP1 cleavage rather than driving maturation as previously postulated. 相似文献
26.
Pressure denaturation of the bacteriophage P22 coat protein and its entropic stabilization in icosahedral shells. 总被引:1,自引:0,他引:1 下载免费PDF全文
The pressure stability of bacteriophage P22 coat protein in both monomeric and polymeric forms under hydrostatic pressure was examined using light scattering, fluorescence emission, polarization, and lifetime methodology. The monomeric protein is very unstable toward pressure and undergoes significant structural changes at pressures as low as 0.5 kbar. These structural changes ultimately lead to denaturation of the subunit. Comparison of the protein denatured by pressure to that in guanidine hydrochloride suggests that pressure results in partial unfolding, perhaps by a domain mechanism. Fluorescence lifetime measurements indicate that at atmospheric pressure the local environments of the tryptophans are remarkably similar, suggesting they may be clustered. In contrast to the monomeric protein subunit, the protein when polymerized into procapsid shells is very stable to applied pressure and does not dissociate with pressure up to 2.5 kbar. However, under applied pressure the procapsid shells are cold-labile, suggesting they are entropically stabilized. The significance of these results in terms of virus assembly are discussed. 相似文献
27.
Sun Y Parker MH Weigele P Casjens S Prevelige PE Krishna NR 《Journal of molecular biology》2000,297(5):1195-1202
Scaffolding proteins are required for high fidelity assembly of most high T number dsDNA viruses such as the large bacteriophages, and the herpesvirus family. They function by transiently binding and positioning the coat protein subunits during capsid assembly. In both bacteriophage P22 and the herpesviruses the extreme scaffold C terminus is highly charged, is predicted to be an amphipathic alpha-helix, and is sufficient to bind the coat protein, suggesting a common mode of action. NMR studies show that the coat protein-binding domain of P22 scaffolding protein exhibits a helix-loop-helix motif stabilized by a hydrophobic core. One face of the motif is characterized by a high density of positive charges that could interact with the coat protein through electrostatic interactions. Results from previous studies with a truncation fragment and the observed salt sensitivity of the assembly process are explained by the NMR structure. 相似文献
28.
The tail of the bacteriophage P22 is composed of multiple protein components and integrates various biological functions that are crucial to the assembly and infection of the phage. The three-dimensional structure of the P22 tail machine determined by electron cryo-microscopy and image reconstruction reveals how the five types of polypeptides present as 51 subunits are organized into this molecular machine through twelve-, six- and three-fold symmetry, and provides insights into molecular events during host cell attachment and phage DNA translocation. 相似文献
29.
J.C. YUSTE J. PEÑUELAS M. ESTIARTE J. GARCIA‐MAS S. MATTANA R. OGAYA M. PUJOL J. SARDANS 《Global Change Biology》2011,17(3):1475-1486
Microbial‐mediated decomposition of soil organic matter (SOM) ultimately makes a considerable contribution to soil respiration, which is typically the main source of CO2 arising from terrestrial ecosystems. Despite this central role in the decomposition of SOM, few studies have been conducted on how climate change may affect the soil microbial community and, furthermore, on how possible climate‐change induced alterations in the ecology of microbial communities may affect soil CO2 emissions. Here we present the results of a seasonal study on soil microbial community structure, SOM decomposition and its temperature sensitivity in two representative Mediterranean ecosystems where precipitation/throughfall exclusion has taken place during the last 10 years. Bacterial and fungal diversity was estimated using the terminal restriction fragment length polymorphism technique. Our results show that fungal diversity was less sensitive to seasonal changes in moisture, temperature and plant activity than bacterial diversity. On the other hand, fungal communities showed the ability to dynamically adapt throughout the seasons. Fungi also coped better with the 10 years of precipitation/throughfall exclusion compared with bacteria. The high resistance of fungal diversity to changes with respect to bacteria may open the controversy as to whether future ‘drier conditions’ for Mediterranean regions might favor fungal dominated microbial communities. Finally, our results indicate that the fungal community exerted a strong influence over the temporal and spatial variability of SOM decomposition and its sensitivity to temperature. The results, therefore, highlight the important role of fungi in the decomposition of terrestrial SOM, especially under the harsh environmental conditions of Mediterranean ecosystems, for which models predict even drier conditions in the future. 相似文献
30.
Elizabeth Kiwanuka Lauren Andersson Edward J Caterson Johan PE Junker Bengt Gerdin Elof Eriksson 《Experimental cell research》2013