Virus Maturation Involving Large Subunit Rotations and Local Refolding

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Science  27 Apr 2001:
Vol. 292, Issue 5517, pp. 744-748
DOI: 10.1126/science.1058069

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Large-scale conformational changes transform viral precursors into infectious virions. The structure of bacteriophage HK97 capsid, Head-II, was recently solved by crystallography, revealing a catenated cross-linked topology. We have visualized its precursor, Prohead-II, by cryoelectron microscopy and modeled the conformational change by appropriately adapting Head-II. Rigid-body rotations (∼40 degrees) cause switching to an entirely different set of interactions; in addition, two motifs undergo refolding. These changes stabilize the capsid by increasing the surface area buried at interfaces and bringing the cross-link–forming residues, initially ∼40 angstroms apart, close together. The inner surface of Prohead-II is negatively charged, suggesting that the transition is triggered electrostatically by DNA packaging.

  • * To whom correspondence should be addressed at Building 6, Room B2-34, 6 Center Drive MSC 2717, NIH, Bethesda, MD 20892–2717, USA. E-mail: alasdair_steven{at}

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