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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
4
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pubmed:dateCreated |
1994-11-2
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pubmed:databankReference | |
pubmed:abstractText |
The bacteriophage T4 late gene wac (whisker's antigen control) encodes a fibrous protein which forms a collar/whiskers complex. Whiskers function as a helper protein for the long tail fibres assembly and plays a role in regulating retraction of the long tail fibres in response to environmental conditions. In this work we show that expression of the cloned wac gene in Escherichia coli yields a protein oligomer of 53 nm length which we call fibritin, and which is able to complement gpwac T4 particles in vitro. CD spectroscopy of fibritin indicates a 90% alpha-helical content, and scanning calorimetry shows that the protein has several distinct domains. The analysis of the 486 amino acid sequence of fibritin reveals three structural components: a 408 amino acid region that contains 12 putative coiled-coil segments with a canonical heptad (a-b-c-d-e-f-g)n substructure where the "a" and "d" positions are preferentially occupied by apolar residues, and the N and C-terminal domains (47 and 29 amino acid residues, respectively) have no heptad substructure. The distribution of hydrophobic residues within heptads is more similar to a triple than to a double coiled-coil. The alpha-helical segments are separated by short "linker" regions, variable in length, that have a high proportion of glycine and proline residues. Each coiled-coil segment has, on the borders with linker regions, residues that are common to the N and C-terminal caps of the alpha-helices. Full-length and amino-terminally truncated fibritins can be reassembled in vitro after temperature-induced denaturation. Co-assembly of full-length fibritin and the N-terminal deletion mutant, as well as analytical centrifugation, indicates that the protein is a parallel triple-standard alpha-helical coiled-coil. Deletions of various N-terminal portions of fibritin did not block trimerisation but the mutant trimers are unable to bind to T4 particles. The last 18 C-terminal residues of fibritin are required for correct trimerisation of gpwac monomers in vivo. We propose that fibritin might serve as a convenient model for the investigation of folding and assembly mechanisms of alpha-fibrous proteins.
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pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical | |
pubmed:status |
MEDLINE
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pubmed:month |
Sep
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pubmed:issn |
0022-2836
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
30
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pubmed:volume |
242
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pubmed:geneSymbol |
wac
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pubmed:owner |
NLM
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pubmed:authorsComplete |
N
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pubmed:pagination |
470-86
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pubmed:dateRevised |
2006-11-15
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pubmed:meshHeading |
pubmed-meshheading:7932704-Amino Acid Sequence,
pubmed-meshheading:7932704-Bacteriophage T4,
pubmed-meshheading:7932704-Base Sequence,
pubmed-meshheading:7932704-Circular Dichroism,
pubmed-meshheading:7932704-DNA, Viral,
pubmed-meshheading:7932704-Escherichia coli,
pubmed-meshheading:7932704-Genes, Viral,
pubmed-meshheading:7932704-Models, Molecular,
pubmed-meshheading:7932704-Molecular Sequence Data,
pubmed-meshheading:7932704-Protein Conformation,
pubmed-meshheading:7932704-Protein Folding,
pubmed-meshheading:7932704-Recombinant Proteins,
pubmed-meshheading:7932704-Sequence Alignment,
pubmed-meshheading:7932704-Thermodynamics,
pubmed-meshheading:7932704-Ultracentrifugation,
pubmed-meshheading:7932704-Viral Proteins
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pubmed:year |
1994
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pubmed:articleTitle |
Fibritin encoded by bacteriophage T4 gene wac has a parallel triple-stranded alpha-helical coiled-coil structure.
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pubmed:affiliation |
Ivanovsky Institute of Virology, Moscow, Russia.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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