Linked Life Data

15210344

Source:http://linkedlifedata.com/resource/pubmed/id/15210344

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2004-6-22
pubmed:abstractText
Bacteriophage capsids are a striking example of a robust yet dynamic genome delivery vehicle. Like most phages, HK97 undergoes a conformational maturation that converts a metastable Prohead into the mature Head state. In the case of HK97, maturation involves a significant expansion of the capsid and concomitant cross-linking of capsid subunits. The final state, termed Head-II, is a 600 angstroms diameter icosahedral structure with catenated subunit rings. Cryo-EM, small angle X-ray scattering (SAXS), and biochemical assays were used previously to characterize the initial (Prohead-II) and final states (Head-II) as well as four maturation intermediates. Here we extend the characterization of the acid-induced expansion of HK97 in vitro by monitoring changes in intrinsic fluorescence, circular dichroism (CD), and SAXS. We find that the greatest changes in all observables occur at an early stage of maturation. Upon acidification, fluorescence emissions from HK97 exhibit a blueshift and decrease in intensity. These spectral changes reveal two kinetic phases of the expansion reaction. The early phase exhibits sensitivity to pH, increasing in rate nearly 200-fold when acidification pH is lowered from 4.5 to 3.9. The second, slower phase reported by fluorescence is relatively insensitive to pH. Time-resolved SAXS experiments report an increase in overall particle dimension that parallels the fluorescence changes for the early phase. Native agarose gel assays corroborated this finding. By contrast, probes of CD at far-UV indicate that secondary structural changes precede the early expansion phase reported by SAXS and fluorescence. Based on the crystallographic structure of Head-II and the pseudo-atomic model of Prohead-II, we interpret these changes as reflecting the conversion of subunit N-terminal arms (N-arm) from unstructured polypeptide to the mixture of beta-strand and beta-turn observed in the Head-II crystal structure. Refolding of the N-arm may thus represent the conformational trigger that initiates the irreversible expansion of the phage capsid.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0022-2836
pubmed:author
pubmed:copyrightInfo
Copyright 2004 Elsevier Ltd.
pubmed:issnType
Print
pubmed:day
9
pubmed:volume
340
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
419-33
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2004
pubmed:articleTitle
Evidence that a local refolding event triggers maturation of HK97 bacteriophage capsid.
pubmed:affiliation
Department of Molecular Biology and Center for Integrative Molecular Biosciences, The Scripps Research Institute, MB-31, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.