A hydrophobic patch on the flap-tip helix of E.coli RNA polymerase mediates sigma(70) region 4 function.
J Mol Biol
; 343(3): 569-87, 2004 Oct 22.
Article
en En
| MEDLINE
| ID: mdl-15465046
ABSTRACT
The Escherichia coli RNA polymerase beta subunit contains a flexible flap domain that interacts with region 4 of sigma(70) to position it for recognition of the -35 element of promoters. We report that this function depends on a hydrophobic patch on one face of the short stretch of alpha helix located at the tip of the flap domain, called the flap-tip helix. Disruption of the hydrophobic patch by the substitution of hydrophilic or charged amino acids resulted in a loss of the interaction between the flap and sigma region 4, as determined by protease sensitivity assays, and impaired transcription from -35-dependent promoters. We suggest that contact of the flap-tip helix hydrophobic patch to the sigma region 4 hydrophobic core is essential for stable interaction of the flap-tip helix with region 4. This contact allowed region 4.2 recognition of the -35 promoter element and appeared to stabilize region 4 interaction with the beta' Zn(2+) binding domain. Our studies failed to detect any role for sigma region 1.1 in establishing or maintaining the flap-sigma region 4 interaction, consistent with recent reports placing sigma region 1.1 in the downstream DNA channel.
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Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Factor sigma
/
ARN Polimerasas Dirigidas por ADN
/
Estructura Secundaria de Proteína
/
Proteínas de Escherichia coli
/
Escherichia coli
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
J Mol Biol
Año:
2004
Tipo del documento:
Article
País de afiliación:
Estados Unidos