Escherichia coli-Salmonella typhimurium hybrid nusA genes: identification of a short motif required for action of the lambda N transcription antitermination protein.
The Escherichia coli nusA gene, nusAEc, encodes an essential protein that influences transcription elongation. Derivatives of E. coli in which the Salmonella typhimurium nusA gene, nusASt, has replaced nusAEc are viable. Thus, NusASt can substitute for NusAEc in supporting essential bacterial activities. However, hybrid E. coli strains with the nusASt substitution do not effectively support transcription antitermination mediated by the N gene product of phage lambda. We report the DNA sequence of nusASt, showing that the derived amino acid sequence is 95% identical to the derived amino acid sequence of nusAEc. The alignment of the amino acid sequences reveals scattered single amino acid differences and one region of significant heterogeneity. In this region, called 449, NusAEc has four amino acids and NusASt has nine amino acids. Functional studies of hybrid nusA genes, constructed from nusAEc and nusASt, show that the 449 region of the NusAEc protein is important for lambda N-mediated transcription antitermination. A hybrid that has a substitution of the four E. coli codons for the nine S. typhimurium codons, but is otherwise nusASt, supports the action of the N antitermination protein. The 449 region and, presumably, adjacent sequences appear to compose a functional domain of NusAEc important for the action of the N transcription antitermination protein of phage lambda.
Craven
M G
MG
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109.
Granston
A E
AE
Schauer
A T
AT
Zheng
C
C
Gray
T A
TA
Friedman
D I
DI
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D017931:DNA Primers; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005816:Genetic Complementation Test; D005838:Genotype; D008969:Molecular Sequence Data; D010445:Peptide Elongation Factors; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic; D015183:Restriction Mapping; D012486:Salmonella typhimurium / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors
D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D010445:Peptide Elongation Factors; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; C068727:nusA protein, E coli