The C-terminal region of the Vibrio fischeri LuxR protein contains an inducer-independent lux gene activating domain.
The Vibrio fischeri luminescence genes are activated by an autoinducer and the 250-amino acid residue LuxR protein. To develop a general view of LuxR structure and function, a set of luxR 5'-deletion mutations was generated. Ten luxR mutant plasmids encoding active LuxR proteins with deletions ranging from residues 2-5 (delta 2-5) to residues 2-182 (delta 2-182) were studied. The degree of transcriptional activation of luminescence genes by the truncated LuxR proteins ranged from 0.01% to greater than 200% of the wild-type level. LuxR proteins with small deletions (up to delta 2-20) were active and remained autoinducer-dependent, LuxR proteins with deletions between residues 2-58 and 2-138 showed low activity and were not affected by autoinducer, and LuxR proteins with large deletions such as the delta 2-162 protein were highly active and autoinducer-independent. However, proteins with deletions equal to or greater than delta 2-20 were unable to autoregulate luxR. Our data indicate there is a C-terminal LuxR domain capable of functioning as a transcriptional activator. We suggest that an N-terminal region of LuxR starting between residues 20 and 58 and extending to the region of residues 138-162 masks the activator function of the C-terminal domain. Residues prior to position 20 are needed for autoregulatory function. Experiments showing that wild-type luxR is dominant over luxR genes coding the delta 2-58 through delta 2-138 proteins indicate the N-terminal arm masks lux DNA binding.
Choi
S H
SH
Department of Microbiology, University of Iowa, Iowa City 52242.
Greenberg
E P
EP
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D008163:Luminescent Measurements; D016296:Mutagenesis; D010957:Plasmids; D012097:Repressor Proteins; D015183:Restriction Mapping; D015534:Trans-Activators; D014158:Transcription, Genetic; D014733:Vibrio / Q000235:genetics*
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; C064778:LuxR autoinducer binding proteins