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Autoregulation of the tufB operon in Salmonella
Author(s) -
Brandis Gerrit,
Bergman Jessica M.,
Hughes Diarmaid
Publication year - 2016
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.13364
Subject(s) - biology , operon , salmonella , genetics , autoregulation , l arabinose operon , lac operon , bacteria , microbiology and biotechnology , gene , escherichia coli , blood pressure , endocrinology
Summary In Salmonella enterica and related species, translation elongation factor EF‐Tu is encoded by two widely separated but near‐identical genes, tufA and tufB . Two thirds of EF‐Tu is expressed from tufA with the remaining one third coming from tufB . Inactivation of tufA is partly compensated by a doubling in the amount of EF‐TuB but the mechanism of this up‐regulation is unknown. By experimental evolution selecting for improved growth rate in a strain with an inactive tufA we selected six different noncoding or synonymous point mutations close to the tufB start codon. Based on these results we constructed a total of 161 different point mutations around the tufB start codon, as well as tufB 3′‐truncations, and measured tufB expression using tufB‐yfp transcriptional and translational fusions. The expression data support the presence of two competing stem‐loop structures that can form in the 5′‐end of the tufB mRNA. Formation of the ‘closed’ structure leads to Rho‐dependent transcriptional termination of the tufB mRNA. We propose a model in which translational speed is used as a sensor for EF‐Tu concentration and where the expression of tufB is post‐transcriptionally regulated. This model describes for the first time how expression of the most abundant Salmonella protein is autoregulated.