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Hk97 maturation studied by crystallography and h/(2)h exchange reveals the structural basis for exothermic particle transitions

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Overview

authors

  • Gertsman, I.
  • Komives, E. A.
  • Johnson Jr., John

publication date

  • March 2010

journal

  • Journal of Molecular Biology  Journal

abstract

  • HK97 is an exceptionally amenable system for characterizing major conformational changes associated with capsid maturation in double-stranded DNA bacteriophage. HK97 undergoes a capsid expansion of approximately 20%, accompanied by major subunit rearrangements during genome packaging. A previous 3.44-A-resolution crystal structure of the mature capsid Head II and cryo-electron microscopy studies of other intermediate expansion forms of HK97 suggested that, primarily, rigid-body movements facilitated the maturation process. We recently reported a 3.65-A-resolution structure of the preexpanded particle form Prohead II (P-II) and found that the capsid subunits undergo significant refolding and twisting of the tertiary structure to accommodate expansion. The P-II study focused on major twisting motions in the P-domain and on refolding of the spine helix during the transition. Here we extend the crystallographic comparison between P-II and Head II, characterizing the refolding events occurring in each of the four major domains of the capsid subunit and their effect on quaternary structure stabilization. In addition, hydrogen/deuterium exchange, coupled to mass spectrometry, was used to characterize the structural dynamics of three distinct capsid intermediates: P-II, Expansion Intermediate, and the nearly mature Head I. Differences in the solvent accessibilities of the seven quasi-equivalent capsid subunits, attributed to differences in secondary and quaternary structures, were observed in P-II. Nearly all differences in solvent accessibility among subunits disappear after the first transition to Expansion Intermediate. We show that most of the refolding is coupled to this transformation, an event associated with the transition from asymmetric to symmetric hexamers.

subject areas

  • Amino Acid Sequence
  • Bacteriophages
  • Capsid Proteins
  • Crystallography, X-Ray
  • Deuterium Exchange Measurement
  • Macromolecular Substances
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Folding
  • Protein Structure, Quaternary
  • Virion
  • Virus Assembly
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Research

keywords

  • X-ray crystallography
  • hydrogen/deuterium exchange
  • mass spectrometry
  • protein folding
  • virus assembly
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Identity

PubMed Central ID

  • PMC2855905

International Standard Serial Number (ISSN)

  • 0022-2836

Digital Object Identifier (DOI)

  • 10.1016/j.jmb.2010.01.016

PubMed ID

  • 20093122
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Additional Document Info

start page

  • 560

end page

  • 574

volume

  • 397

issue

  • 2

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