ジャーナル: J Virol / 年: 2009 タイトル: Association of the pr peptides with dengue virus at acidic pH blocks membrane fusion. 著者: I-M Yu / H A Holdaway / P R Chipman / R J Kuhn / M G Rossmann / J Chen / 要旨: Flavivirus assembles into an inert particle that requires proteolytic activation by furin to enable transmission to other hosts. We previously showed that immature virus undergoes a conformational ...Flavivirus assembles into an inert particle that requires proteolytic activation by furin to enable transmission to other hosts. We previously showed that immature virus undergoes a conformational change at low pH that renders it accessible to furin (I. M. Yu, W. Zhang, H. A. Holdaway, L. Li, V. A. Kostyuchenko, P. R. Chipman, R. J. Kuhn, M. G. Rossmann, and J. Chen, Science 319:1834-1837, 2008). Here we show, using cryoelectron microscopy, that the structure of immature dengue virus at pH 6.0 is essentially the same before and after the cleavage of prM. The structure shows that after cleavage, the proteolytic product pr remains associated with the virion at acidic pH, and that furin cleavage by itself does not induce any major conformational changes. We also show by liposome cofloatation experiments that pr retention prevents membrane insertion, suggesting that pr is present on the virion in the trans-Golgi network to protect the progeny virus from fusion within the host cell.
pH: 6 / 詳細: 6 mM Tris-HCL, 25 mM MES, 120 mM NaCl, 1 mM EDTA
凍結
凍結剤: ETHANE / 装置: OTHER 手法: A small vial of ethane is placed inside a larger liquid nitrogen reservoir. The grid holding a few microliters of the sample is held in place at the bottom of a plunger by the means of fine ...手法: A small vial of ethane is placed inside a larger liquid nitrogen reservoir. The grid holding a few microliters of the sample is held in place at the bottom of a plunger by the means of fine tweezers. Once the ethane in the vial is completely frozen, it needs to be slightly melted. When the liquid ethane is ready, a piece of filter paper is then pressed against the sample to blot of excess buffer, sufficient to leave a thin layer on the grid. After a predetermined time, the filter paper is removed, and the plunger is allowed to drop into the liquid ethane. Once the grid enters the liquid ethane, the sample is rapidly frozen, and the grid is transferred under liquid nitrogen to a storage box immersed liquid nitrogen for later use in the microscope.