We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Crosslinking renders bacteriophage HK97 capsid maturation irreversible and effects an essential stabilization.
- Authors
Ross, Philip D; Naiqian Cheng; Conway, James F; Firek, Brian A; Hendrix, Roger W; Duda, Robert L; Steven, Alasdair C
- 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, 30Åfrom 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.
- Subjects
BACTERIOPHAGES; VIRUSES; DENATURATION of proteins; PROTEIN crosslinking; MOLECULAR biology
- Publication
EMBO Journal, 2005, Vol 24, Issue 7, p1352
- ISSN
0261-4189
- Publication type
Article
- DOI
10.1038/sj.emboj.7600613