Journal
JOURNAL OF INORGANIC BIOCHEMISTRY
Volume 203, Issue -, Pages -Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.jinorgbio.2019.110889
Keywords
Multiheme proteins; cbb(3) oxidase; Reduction potentials; Redox partners; Electron transfer
Funding
- Dartmouth Office of the Provost
- NIH COBRE Institute for Biomolecular targeting at Dartmouth [P20 GM113132]
- National Institute of Health, National Institute of General Medical Sciences [P41GM111244]
- DOE Office of Biological and Environmental Research [KP1605010]
- DOE Office of Basic Energy Sciences [DE-SC0012704 (KC0401040)]
- FEDER through COMPETE 2020 [022161]
- FEDER through POCI [022161]
- FEDER through PORL [022161]
- FCT through PIDDAC [022161]
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At low oxygen concentrations, respiration of Pseudomonas aeruginosa (Pa) and other bacteria relies on activity of cytochrome cbb(3) oxidases. A diheme cytochrome c(4) (cyt c(4)) donates electrons to Pa cbb3 oxidases to enable oxygen reduction and proton pumping by these enzymes. Given the importance of this redox pathway for bacterial pathogenesis, both cyt c(4) and cbb(3) oxidase are potential targets for new antibacterial strategies. The structural information about these two proteins, however, is scarce, and functional insights for Pa and other bacteria have been primarily drawn from analyses of the analogous system from Pseudomonas stutzeri (Ps). Herein, we describe characterization of structural and redox properties of cyt c(4) from Pa. The crystal structure of Pa cyt c(4) has revealed that this protein is organized in two monoheme domains. The interdomain interface is more hydrophobic in Pa cyt c(4), and the protein surface does not show the dipolar distribution of charges found in Ps cyt c(4). The reduction potentials of the two hemes are similar in Pa cyt c(4) but differ by about 100 mV in Ps cyt c(4). Analyses of structural models of these and other cyt c(4) proteins suggest that multiple factors contribute to the potential difference of the two hemes in these proteins, including solvent accessibility of the heme group, the distribution of surface charges, and the nature of the interdornain interface. The distinct properties of cyt c(4) proteins from closely-related Pa and Ps bacteria emphasize the importance of examining the cbb(3)/cyt c(4) redox pathway in multiple species.
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