Evidence that asgB encodes a DNA-binding protein essential for growth and development of Myxococcus xanthus.
The asg mutants of Myxococcus xanthus are defective in production of extracellular A-signal, which serves as a cell density signal for fruiting-body development. The DNA sequence of asgB, one of the three asg genes, was determined. The deduced amino acid sequence of AsgB contains a DNA-binding helix-turn-helix motif near the C terminus. This putative helix-turn-helix is highly similar to the helix-turn-helix in region 4.2 of major sigma factors, which is the region that recognizes and interacts with -35 sequences of promoters. We propose that AsgB is a transcription factor that binds to DNA sequences similar to the -35 hexamer, TTGACA. Analyses of asgB RNA levels and expression of an asgB-lacZ translational fusion indicate that expression of asgB remains fairly constant during the transition from growth into early development. The mutation within the asgB480 allele was identified as an A-to-G transition that results in a threonine-to-alanine substitution in the predicted protein product. Attempts to replace the wild-type copy of asgB with a null allele failed, indicating that asgB may be essential for growth.
Plamann
L
L
Department of Biology, Texas A&M University, College Station 77843-3258.
Davis
J M
JM
Cantwell
B
B
Mayor
J
J
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D002450:Cell Communication / Q000235:genetics*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D007291:Inosine Monophosphate / Q000096:biosynthesis; D008969:Molecular Sequence Data; D009154:Mutation; D016941:Myxococcus xanthus / Q000235:genetics* / Q000254:growth & development; D016366:Open Reading Frames / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*
C086516:AsgB protein, Myxococcus xanthus; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D007291:Inosine Monophosphate