Physiological role and redox properties of a small cytochrome c_5, cytochrome c-552, from alkaliphile, Pseudomonas alcaliphila AL15-21^T(MICROBIAL PHYSIOLOGY AND BIOTECHNOLOGY)

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Cytochrome c-552 from Pseudomonas alcaliphila AL15-21^T, which is a small cytochrome c_5 from Pseudomonas spp., was first purified and characterized in our previous study. Although it has been found that cytochrome c-552 is induced at a high pH under air-limited condition, the physiological role of this cytochrome c has not been clarified yet. Therefore, to understand its physiological role, further characterization of this cytochrome expressed in Escherichia coli was performed. The yield of the recombinant protein reached 2.8mg/l of culture, which was 76.4-fold larger than that of native cells. Analytical data of the recombinant protein exactly agreed with that of native cytochrome c-552. The recombinant cytochrome c-552 was oxidized by partially purified cb-type cytochrome c oxidase from P. alcaliphila AL15-21^T at a rate of 9.6μ mol min^<-1>mg oxidase^<-1>. Unlike reported cytochromes c from other Pseudomonas spp., the E°' values between pHs 5.0 and 10.0 were nearly unchanged. Cytochrome c-552 oxidized very slowly at pHs 8.0(6.1×10^<-4>h^<-1>), 9.0(1.4×10^<-3>h^<-1>) and 10.0(1.6×10^<-3>h^<-1>), whereas it oxidized more rapidly at pH 7.0(2.5×10^<-3>h^<-1>). On the other hand, horse heart cytochrome c showed higher oxidation rates at pHs 6.0-10.0 than cytochrome c-552. It is considered that the high electron-retaining ability of cytochrome c-552 at high pHs is important for its physiological function in the environmental adaptation of this bacteria for superior growth at high pHs under air-limited conditions.

Physiological role and redox properties of a small cytochrome c_5, cytochrome c-552, from alkaliphile, Pseudomonas alcaliphila AL15-21^T(MICROBIAL PHYSIOLOGY AND BIOTECHNOLOGY)

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