Article
- The EMBO Journal (2005) 24, 1352 - 1363
- doi:10.1038/sj.emboj.7600613
Published online: 17 March 2005
Subject Categories:
Crosslinking renders bacteriophage HK97 capsid maturation irreversible and effects an essential stabilization
Philip D Ross1, Naiqian Cheng2, James F Conway3, Brian A Firek4, Roger W Hendrix4, Robert L Duda4 and Alasdair C Steven2
- Laboratory of Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, MD, USA
- Laboratory of Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, Bethesda, MD, USA
- Institut de Biologie Structurale CEA-CNRS-UJF, Grenoble, France
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
Correspondence to:
Alasdair C Steven, Building 50, Room 1517, 50 South Drive MSC 8025, NIH, Bethesda, MD 20892, USA. Tel.: +1 301 443 7651; Fax: +1 301 496 0132; E-mail: alasdair_steven@nih.gov
Received 1 December 2004; Accepted 10 February 2005
Abstract
In HK97 capsid maturation, structural change ('expansion') is accompanied by formation of covalent crosslinks, connecting residue K169 in the 'E-loop' of each subunit with N356 on another subunit. We show by complementation experiments with the K169Y mutant, which cannot crosslink, that crosslinking is an essential function. The precursor Prohead-II passes through three expansion intermediate (EI) states en route to the end state, Head-II. We investigated the effects of expansion and crosslinking on stability by differential scanning calorimetry of wild-type and K169Y capsids. After expansion, the denaturation temperature (Tp) of K169Y capsids is slightly reduced, indicating that their thermal stability is not enhanced, but crosslinking effects a major stabilization (
Tp, +11°C). EI-II is the earliest capsid to form crosslinks. Cryo-electron microscopy shows that for both wild-type and K169Y EI-II, most E-loops are in the 'up' position, 30 Å from the nearest N356: thus, crosslinking in EI-II represents capture of mobile E-loops in 'down' positions. At pH 4, most K169Y capsids remain as EI-II, whereas wild-type capsids proceed to EI-III, suggesting that crosslink formation drives maturation by a Brownian ratchet mechanism.
Keywords:
- Brownian ratchet,
- conformational change,
- cryo-electron microscopy,
- differential scanning calorimetry,
- virus assembly
MORE ARTICLES LIKE THIS
These links to content published by NPG are automatically generated
RESEARCH
An unexpected twist in viral capsid maturation
Nature Letters to Editor (02 Apr 2009)
Dynamics of herpes simplex virus capsid maturation visualized by time-lapse cryo-electron microscopy
Nature Structural Biology Article (01 May 2003)
Structural changes of bacteriophage φ29 upon DNA packaging and release
The EMBO Journal Article (01 Nov 2006)
Coat protein fold and maturation transition of bacteriophage P22 seen at subnanometer resolutions
Nature Structural Biology Article (01 Feb 2003)
Maturation of phage T7 involves structural modification of both shell and inner core components
The EMBO Journal Article (02 Nov 2005)
