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Fig. 5 | Journal of Biomedical Science

Fig. 5

From: The fciTABC and feoABI systems contribute to ferric citrate acquisition in Stenotrophomonas maltophilia

Fig. 5

Comparisons of the ferric citrate acquisition systems between E. coli, P. aeruginosa, and S. maltophilia. A The ferric citrate acquisition system of E. coli. Ferric citrate is translocated into the periplasm through the TonB-dependent outer membrane receptor FecA. Meanwhile, the ferric citrate-FecA interaction results in a signal transmission from FecA, via the inner membrane-spanning FecR, to the cytoplasmic sigma factor FecI. FecI then directs the expression of the fecABCDE operon. In the periplasm, FecB shuttles ferric citrate into the cytoplasm through the inner membrane transport system FecC/D/E. B The ferric citrate acquisition system of P. aeruginosa. Ferric citrate is translocated into the periplasm via FecA and initiates the signaling transduction via FecR to FecI. FeoB is an inner membrane transporter responsible for citrate-mediated iron acquisition. The model suggests that the ferric iron, released from ferric citrate, in the periplasm is reduced to ferrous iron and subsequently transported into the cytosol via FeoB. C The ferric citrate acquisition system of S. maltophilia. Ferric citrate is translocated into the periplasm via FciA. Ferric citrate is then transported across the inner membrane via the FeoABI inner membrane transporter system. The fciA gene is a member of the fciTABC operon. FciT and FciC, but not FciB, participate in citrate-mediated iron acquisition. FeoI can modulates the FeoB-mediated ferric citrate transportation via an intra-membrane protein–protein interaction

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