ssaD1, a suppressor of secA51(Ts) that renders growth of Escherichia coli cold sensitive, is an early amber mutation in the transcription factor gene nusB.
Complementation analysis of the ssaD1 mutation, isolated as a suppressor of the secA51(Ts) mutation that renders growth of Escherichia coli cold sensitive, was used to show that ssaD corresponds to nusB, a gene known to be important in transcription antitermination. DNA sequence analysis of the ssaD1 allele showed that it creates an amber mutation in the 15th codon of nusB. Analysis of the effect of different levels of NusB protein on secA transcription and translation suggested that NusB plays little or no role in the control of secA expression. Accordingly, mechanisms by which nusB inactivation can lead to suppression of secA51(Ts) and secY24(Ts) mutations without affecting secA expression need to be considered.
Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459.
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D000251:Adenosine Triphosphatases / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003080:Cold Temperature; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016153:Genes, Suppressor; D005816:Genetic Complementation Test; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D014176:Protein Biosynthesis; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; C074952:NusB protein, E coli; D000069816:SEC Translocation Channels; D014157:Transcription Factors; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins