TstI, a Type II restriction-modification protein with DNA recognition, cleavage and methylation functions in a single polypeptide.
Nucleic Acids Res
; 42(9): 5809-22, 2014 May.
Article
em En
| MEDLINE
| ID: mdl-24634443
ABSTRACT
Type II restriction-modification systems cleave and methylate DNA at specific sequences. However, the Type IIB systems look more like Type I than conventional Type II schemes as they employ the same protein for both restriction and modification and for DNA recognition. Several Type IIB proteins, including the archetype BcgI, are assemblies of two polypeptides one with endonuclease and methyltransferase roles, another for DNA recognition. Conversely, some IIB proteins express all three functions from separate segments of a single polypeptide. This study analysed one such single-chain protein, TstI. Comparison with BcgI showed that the one- and the two-polypeptide systems differ markedly. Unlike the heterologous assembly of BcgI, TstI forms a homotetramer. The tetramer bridges two recognition sites before eventually cutting the DNA in both strands on both sides of the sites, but at each site the first double-strand break is made long before the second. In contrast, BcgI cuts all eight target bonds at two sites in a single step. TstI also differs from BcgI in either methylating or cleaving unmodified sites at similar rates. The site may thus be modified before TstI can make the second double-strand break. TstI MTase acts best at hemi-methylated sites.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Thermus
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Proteínas de Bactérias
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Desoxirribonucleases de Sítio Específico do Tipo II
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Metilação de DNA
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Clivagem do DNA
Idioma:
En
Revista:
Nucleic Acids Res
Ano de publicação:
2014
Tipo de documento:
Article
País de afiliação:
Reino Unido