Role of the RNA polymerase trigger loop in catalysis and pausing.
Nat Struct Mol Biol
; 17(1): 99-104, 2010 Jan.
Article
em En
| MEDLINE
| ID: mdl-19966797
ABSTRACT
The trigger loop (TL) is a polymorphous component of RNA polymerase (RNAP) that makes direct substrate contacts and promotes nucleotide addition when folded into an alpha-helical hairpin (trigger helices, TH). However, the roles of the TL/TH in transcript cleavage, catalysis, substrate selectivity and pausing remain ill defined. Based on in vitro assays of Escherichia coli RNAP bearing specific TL/TH alterations, we report that neither intrinsic nor regulator-assisted transcript cleavage of backtracked RNA requires formation of the TH. We find that the principal contribution of TH formation to rapid nucleotidyl transfer is steric alignment of the reactants rather than acid-base catalysis, and that the TL/TH cannot be the sole contributor to substrate selectivity. The similar effects of TL/TH substitutions on pausing and nucleotide addition provide additional support for the view that TH formation is rate-limiting for escape from nonbacktracked pauses.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Transcrição Gênica
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RNA Polimerases Dirigidas por DNA
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Modelos Moleculares
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Estrutura Secundária de Proteína
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Subunidades Proteicas
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Escherichia coli
Idioma:
En
Revista:
Nat Struct Mol Biol
Assunto da revista:
BIOLOGIA MOLECULAR
Ano de publicação:
2010
Tipo de documento:
Article
País de afiliação:
Estados Unidos