Abstract
The genetic element pSSVx from Sulfolobus islandicus, strain REY15/4, is a hybrid between a plasmid and a fusellovirus. This plasmid-virus hybrid infects several species of the hyperthermophilic acidophilic crenarchaeon Sulfolobus. The open reading frame orfc68 of pSSVx encodes a 7.7 kDa protein that does not show significant sequence homology with any protein with known three-dimensional structure. EMSA (electrophoretic mobility-shift assay) experiments, DNA footprinting and CD analyses indicate that recombinant C68, purified from Escherichia coli, binds to two different operator sites that are located upstream of its own promoter. The three-dimensional structure, solved by a single-wavelength anomalous diffraction experiment on a selenomethionine derivative, shows that the protein assumes a swapped-hairpin fold, which is a distinctive fold associated with a family of prokaryotic transcription factors, such as AbrB from Bacillus subtilis. Nevertheless, C68 constitutes a novel representative of this family because it shows several peculiar structural and functional features.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Crystallography, X-Ray
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DNA Footprinting
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DNA, Intergenic / metabolism
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / isolation & purification
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DNA-Binding Proteins / metabolism
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Dimerization
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Fuselloviridae / genetics
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Fuselloviridae / metabolism*
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Molecular Sequence Data
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Operator Regions, Genetic
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Plasmids / genetics
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Plasmids / metabolism*
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Promoter Regions, Genetic
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Protein Conformation
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Recombinant Proteins / chemistry
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Recombinant Proteins / isolation & purification
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Recombinant Proteins / metabolism
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Satellite Viruses / genetics
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Satellite Viruses / metabolism
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Selenomethionine / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
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Sulfolobus / metabolism
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Sulfolobus / virology*
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Transcription Factors / chemistry*
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Transcription Factors / genetics
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Transcription Factors / isolation & purification
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Transcription Factors / metabolism*
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Viral Proteins / chemistry*
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Viral Proteins / genetics
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Viral Proteins / isolation & purification
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Viral Proteins / metabolism*
Substances
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DNA, Intergenic
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DNA-Binding Proteins
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Recombinant Proteins
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Transcription Factors
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Viral Proteins
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Selenomethionine