Publications by authors named "Liliana Moura Massis"

2 Publications

  • Page 1 of 1

A Salmonella Typhi RNA thermosensor regulates virulence factors and innate immune evasion in response to host temperature.

PLoS Pathog 2021 Mar 2;17(3):e1009345. Epub 2021 Mar 2.

Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America.

Sensing and responding to environmental signals is critical for bacterial pathogens to successfully infect and persist within hosts. Many bacterial pathogens sense temperature as an indication they have entered a new host and must alter their virulence factor expression to evade immune detection. Using secondary structure prediction, we identified an RNA thermosensor (RNAT) in the 5' untranslated region (UTR) of tviA encoded by the typhoid fever-causing bacterium Salmonella enterica serovar Typhi (S. Typhi). Importantly, tviA is a transcriptional regulator of the critical virulence factors Vi capsule, flagellin, and type III secretion system-1 expression. By introducing point mutations to alter the mRNA secondary structure, we demonstrate that the 5' UTR of tviA contains a functional RNAT using in vitro expression, structure probing, and ribosome binding methods. Mutational inhibition of the RNAT in S. Typhi causes aberrant virulence factor expression, leading to enhanced innate immune responses during infection. In conclusion, we show that S. Typhi regulates virulence factor expression through an RNAT in the 5' UTR of tviA. Our findings demonstrate that limiting inflammation through RNAT-dependent regulation in response to host body temperature is important for S. Typhi's "stealthy" pathogenesis.
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http://dx.doi.org/10.1371/journal.ppat.1009345DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7954313PMC
March 2021

Evidence of ball-and-chain transport of ferric enterobactin through FepA.

J Biol Chem 2007 Jan 20;282(1):397-406. Epub 2006 Oct 20.

Department of Chemistry & Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, USA.

The Escherichia coli iron transporter, FepA, has a globular N terminus that resides within a transmembrane beta-barrel formed by its C terminus. We engineered 25 cysteine substitution mutations at different locations in FepA and modified their sulfhydryl side chains with fluorescein maleimide in live cells. The reactivity of the Cys residues changed, sometimes dramatically, during the transport of ferric enterobactin, the natural ligand of FepA. Patterns of Cys susceptibility reflected energy- and TonB-dependent motion in the receptor protein. During transport, a residue on the normally buried surface of the N-domain was labeled by fluorescein maleimide in the periplasm, providing evidence that the transport process involves expulsion of the globular domain from the beta-barrel. Porin deficiency much reduced the fluoresceination of this site, confirming the periplasmic labeling route. These data support the previously proposed, but never demonstrated, ball-and-chain theory of membrane transport. Functional complementation between a separately expressed N terminus and C-terminal beta-barrel domain confirmed the feasibility of this mechanism.
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http://dx.doi.org/10.1074/jbc.M605333200DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2398697PMC
January 2007