Novel DNA binding protein SarZ contributes to virulence in Staphylococcus aureus

Authors

  • Chikara Kaito,

    1. Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 3-1, 7-Chome, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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  • Daisuke Morishita,

    1. Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 3-1, 7-Chome, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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  • Yasuhiko Matsumoto,

    1. Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 3-1, 7-Chome, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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  • Kenji Kurokawa,

    1. Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 3-1, 7-Chome, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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  • Kazuhisa Sekimizu

    Corresponding author
      *E-mail sekimizu@mol.f.u-tokyo.ac.jp; Tel. (+81) 358 414 820; Fax (+81) 356 842 973.
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  • The nucleotide sequence of the sarZ gene of RN4220 was deposited in GenBank database under GenBank Accession Number AB251456. The amino acid sequence of B. subtilis OhrR (CAB13172.1) was obtained from the Genome Information Broker program from the DNA Data Bank of Japan (http://gib.genes.nig.ac.jp/). Other amino acid sequences were obtained from GenBank: S. aureus MgrA (AY266422), E. coli MarR (P27245), P. aeruginosa MexR (U23748), S. aureus SarA (U20782).

*E-mail sekimizu@mol.f.u-tokyo.ac.jp; Tel. (+81) 358 414 820; Fax (+81) 356 842 973.

Summary

We previously reported that the cvfA gene is a virulence regulatory gene in Staphylococcus aureus. Here, we identified a novel gene named sarZ that acts as a multicopy suppressor of decreased haemolysin production in the cvfA deletion mutant. The amount of sarZ transcripts was decreased in the cvfA mutant. The sarZ-deletion mutant produced less haemolysin and attenuated virulence in a silkworm-infection model and a mouse-infection model. The amino acid sequence of the sarZ gene product had 19% identity with the transcription factor MarR in Escherichia coli, and the internal region contained a winged helix–turn–helix motif (wHTH), a known DNA binding domain. Purified recombinant SarZ protein had binding affinity for the promoter region of the hla gene that encodes α-haemolysin. SarZ mutant proteins with an amino acid substitution in the N-terminal region or in the wHTH motif had significantly decreased DNA binding. The mutated sarZ genes encoding SarZ mutant proteins with a low affinity for DNA did not complement the decreased haemolysin production or the attenuated killing ability against silkworms in the sarZ mutant. These results suggest that the DNA binding activity of the SarZ protein is required for virulence in S. aureus.

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