Acid-induced structural changes in human rhinovirus 14: possible role in uncoating (original) (raw)
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Human rhinovirus mutants resistant to low pH
Virology, 1991
Mutants of human rhinovirus serotype 14 (HRV14) with increased resistance to treatment at low pH were obtained by repeated cycles of exposure to pH 4.5 and propagation in HeLa cells. Whereas wild-type virus lost more than 5 logs of infectivity upon incubation at pH 4.3, the three isolates examined were essentially unaffected. Conformational change of the viral capsid upon exposure to low pH was assessed as an increase of hydrophobicity by partition between an aqueous phase and a Triton X-l 14 phase; the mutants required exposure to a much lower pH to accumulate in the Triton phase than wild-type HRV14. The sequence of the capsid region was determined for three isolates; two isolates were found to have the changes Thr17 to Ile in VP2 and Asnl 00 to Ile in VP1 . The third isolate also had the change Thr17 to Ile in VP2; however, in VP1 , Asp1 01 was replaced by Glu. Separate introduction of the mutations into full length cDNA clones of the wild-type sequence of HRV14 showed that only the changes in VP1 were necessary for the increased stability at pH 4.5. The implications of the mutations for the three-dimensional structure of the viral capsid are discussed:
Journal of Virology, 2009
The minor receptor group human rhinovirus type 2 enters host cells by endocytosis via members of the low-density-lipoprotein receptor family. In late endosomes, it undergoes a conformational change solely induced by a pH of ≤5.6, resulting in RNA transfer across the endosomal membrane into the cytoplasm. To determine potential driving forces of this process, we investigated whether RNA penetration might depend on the pH gradient and/or the membrane potential between the acidic endosome lumen and the neutral cytoplasm. Since these parameters are difficult to assess in endosomes, we took advantage of the possibility of inducing structural changes, RNA release, and consequently infection from the plasma membrane. To manipulate the pH gradient, cell-bound virus was exposed to membrane-permeant or -impermeant acidic buffers at 4°C, and this was followed by a shift to 34°C in medium containing bafilomycin to prevent RNA release from endosomes. To manipulate the plasma membrane potential, ...
Journal of Virology, 2003
Intercellular adhesion molecule 1 (ICAM-1) functions as the cellular receptor for the major group of human rhinoviruses, being not only the target of viral attachment but also the mediator of viral uncoating. The configurations of HRV3-ICAM-1 complexes prepared both at 4°C and physiological temperature (37°C) were analyzed by cryoelectron microscopy and image reconstruction. The particle diameters of two complexes (with and without RNA) representing uncoating intermediates generated at 37°C were each 4% larger than that of those prepared at 4°C. The larger virus particle arose by an expansive movement of the capsid pentamers along the fivefold axis, which loosens interprotomer contacts, particularly at the canyon region where the ICAM-1 receptor bound. Particle expansion required receptor binding and preceded the egress of the viral RNA. These observations suggest that receptor-mediated uncoating could be a consequence of restrained capsid motion, where the bound receptors maintain ...
Antibody-induced uncoating of human rhinovirus B14
Proceedings of the National Academy of Sciences of the United States of America, 2017
Rhinoviruses (RVs) are the major causes of common colds in humans. They have a nonenveloped, icosahedral capsid surrounding a positive-strand RNA genome. Here we report that the antigen-binding (Fab) fragment of a neutralizing antibody (C5) can trigger genome release from RV-B14 to form emptied particles and neutralize virus infection. Using cryo-electron microscopy, structures of the C5 Fab in complex with the full and emptied particles have been determined at 2.3 Å and 3.0 Å resolution, respectively. Each of the 60 Fab molecules binds primarily to a region on viral protein 3 (VP3). Binding of the C5 Fabs to RV-B14 results in significant conformational changes around holes in the capsid through which the viral RNA might exit. These results are so far the highest resolution view of an antibody-virus complex and elucidate a mechanism whereby antibodies neutralize RVs and related viruses by inducing virus uncoating.
Structural Analysis of Coxsackievirus A7 Reveals Conformational Changes Associated with Uncoating
Journal of Virology, 2012
Coxsackievirus A7 (CAV7) is a rarely detected and poorly characterized serotype of the Enterovirus species Human enterovirus A (HEV-A) within the Picornaviridae family. The CAV7-USSR strain has caused polio-like epidemics and was originally thought to represent the fourth poliovirus type, but later evidence linked this strain to the CAV7-Parker prototype. Another isolate, CAV7-275/58, was also serologically similar to Parker but was noninfectious in a mouse model. Sequencing of the genomic region encoding the capsid proteins of the USSR and 275/58 strains and subsequent comparison with the corresponding amino acid sequences of the Parker strain revealed that the Parker and USSR strains are nearly identical, while the 275/58 strain is more distant. Using electron cryomicroscopy and three-dimensional image reconstruction, the structures of the CAV7-USSR virion and empty capsid were resolved to 8.2-Å and 6.1-Å resolutions, respectively. This is one of the first detailed structural analyses of the HEV-A species. Using homology modeling, reconstruction segmentation, and flexible fitting, we constructed a pseudoatomic T ؍ 1 (pseudo T ؍ 3) model incorporating the three major capsid proteins (VP1 to VP3), addressed the conformational changes of the capsid and its constituent viral proteins occurring during RNA release, and mapped the capsid proteins' variable regions to the structure. During uncoating, VP4 and RNA are released analogously to poliovirus 1, the interfaces of VP2 and VP3 are rearranged, and VP1 rotates. Variable regions in the capsid proteins were predicted to map mainly to the surface of VP1 and are thus likely to affect the tropism and pathogenicity of CAV7.
Crystallization of a common cold virus, human rhinovirus 14: "Isomorphism" with poliovirus crystals
Proceedings of the National Academy of Sciences, 1983
Crystals of rhinovirus 14 have been grown reproducibly. They diffract x-rays to a resolution of at least 3.5 Å. The orthorhombic crystal unit cell contains two virions, each situated on a crystallographic twofold axis. At less than 30-Å resolution, the space group approximates to 1 222 with the particles possessing 222 pseudo crystallographic symmetry. The crystals are “isomorphous” with type I polio crystals [Finch, J. T. & Klug, A. (1959) Nature ( London ) 183, 1709-1714; Hogle, J. M. (1982) J. Mol. Biol. 160, 663-668], suggesting some similarities of structure between enteroviruses and rhinoviruses.