The cue regulon controls both aerobic and anaerobic copper resistance in Salmonella

LUCAS B. PONTEL, LUCIANO ABRIATA, ALEJANDRO VILA, FERNANDO C. SONCINI

Aguas de Lindoia Brasil

Congreso; XXXVIII Reunião Anual da Sociedad Brasilera de Bioquímica y Biología Molecular; 2009

Sociedad Brasilera de Bioquímica y Biología Molecular

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Arial","sans-serif"; mso-fareast-font-family:"Times New Roman"; color:blue; mso-ansi-language:PT; mso-fareast-language:PT-BR;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Copper resistance in Gram-negative bacteria is primarily controlled by the cue regulon. This regulon is composed by the Cu(I) sensor/regulator CueR that induces the expression of two target genes, copA and cueO, coding for an integral inner-membrane Cu-transporting P-type ATPase, and a periplasmic oxygen-dependent multicopper-Cu(I) oxidase, respectively. Escherichia coli also relies on the cus system to increase copper resistance under anaerobic conditions. This system is composed by the CusCFBA efflux pump, which is transcriptionally controlled by the two-component system CusR/CusS. Interestingly, Salmonella harbours all the cue components but lacks the cus locus. Despite of this, Salmonella displays higher resistance to copper than E. coli in anaerobic conditions. We have uncovered a novel, Salmonella-specific, CueR-regulated gene, cueP, coding for a protein that increases resistance to copper both in aerobic and anaerobic conditions. To test whether CueP could functionally substitute the E. coli cus system for copper resistance, we replaced the entire E. coli chromosomal cus locus for the wild-type copy of the Salmonella cueP, including its own promoter. CueR-dependent expression of cueP increased resistance to copper in this engineered strain. Moreover, overexpression of CueP completely restored resistance to copper in a cueR cus double mutant strain in aerobic conditions. Atomic absorption spectrometry, as well as UV-visible spectroscopy demonstrated that CueP is able to bind two Cu(II) equivalents per monomer, supporting a role of CueP as a copper-resistance factor. Our results indicate that in contrast to other enterobacterial species Salmonella has evolved a single pathway to respond to copper excess both in aerobic and anaerobic conditions.