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Titolo:
THE POSSIBLE ROLES OF RESIDUE-79 AND RESIDUE-80 OF THE TRP REPRESSOR FROM ESCHERICHIA-COLI-K-12 IN TRP OPERATOR RECOGNITION
Autore:
GUNES C; STAACKE D; VONWILCKENBERGMANN B; MULLERHILL B;
Indirizzi:
UNIV COLOGNE,INST GENET,WEYERTAL 121 D-50931 COLOGNE GERMANY UNIV COLOGNE,INST GENET D-50931 COLOGNE GERMANY
Titolo Testata:
MGG. Molecular & general genetics
fascicolo: 2, volume: 246, anno: 1995,
pagine: 180 - 195
SICI:
0026-8925(1995)246:2<180:TPRORA>2.0.ZU;2-M
Fonte:
ISI
Lingua:
ENG
Soggetto:
PROTEIN-DNA RECOGNITION; LAC REPRESSOR; TRYPTOPHAN REPRESSOR; CRO REPRESSOR; SECONDARY STRUCTURE; BINDING DOMAINS; TANDEM BINDING; COMPLEX; RESOLUTION; AROH;
Keywords:
TRP REPRESSOR; TRP OPERATOR; HELIX-TURN-HELIX MOTIF; PROTEIN-DNA RECOGNITION; ESCHERICHIA COLI K-12;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
66
Recensione:
Indirizzi per estratti:
Citazione:
C. Gunes et al., "THE POSSIBLE ROLES OF RESIDUE-79 AND RESIDUE-80 OF THE TRP REPRESSOR FROM ESCHERICHIA-COLI-K-12 IN TRP OPERATOR RECOGNITION", MGG. Molecular & general genetics, 246(2), 1995, pp. 180-195

Abstract

We constructed mutans of the Trp repressor from Escherichia coli K-12with all possible single amino acid exchanges at positions 79 and 80 (residues 1 and 2 of the recognition helix). We tested these mutants in vivo by measuring the repression of synthesis of beta-galactosidase with symmetric variants of alpha- and beta-centered trp operators, which replace the lac operator in a synthetic lac system. The Trp repressor carrying a substitution of isoleucine 79 by lysine, showed a markedspecificity change with respect to base pair 7 of the alpha-centered trp operator. Gel retardation experiments confirmed this result. Trp repressor mutant IR79 specifically recognizes a trp operator variant with substitutions in positions 7 and 8. Another mutant, with glycine inposition 79, exhibited loss of contact at base pair 7. We speculate that the side chain of Ile79 interacts with the AT base pairs 7 and 8 of the alpha-centered trp operator, possibly with the methyl groups of thymines. Replacement of thymine in position 7 or 8 by uracil confirmsthe involvement of the methyl group of thymine 8 in repressor binding. Several Trp repressor mutants in position 80 (i.e. AI80, AL80, AM80 and AP80) broaden the specificity of the Trp repressor for alpha-centered trp operator variants with exchanges in positions 3, 4, and 5.

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Documento generato il 20/09/20 alle ore 00:23:28