Characteristics of the aerobic respiratory chains of the microaerophiles Campylobacter jejuni and Helicobacter pylori
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MINI-REVIEW
Mark A. Smith · Moshe Finel · Victoria Korolik · George L. Mendz
Characteristics of the aerobic respiratory chains of the microaerophiles Campylobacter jejuni and Helicobacter pylori
Received: 3 January 2000 / Revised: 3 May 2000 / Accepted: 4 May 2000 / Published online: 17 June 2000 © Springer-Verlag 2000
Abstract The respiratory chain enzymes of microaerophilic bacteria should play a major role in their adaptation to growth at low oxygen tensions. The genes encoding the putative NADH:quinone reductases (NDH-1), the ubiquinol:cytochrome c oxidoreductases (bc1 complex) and the terminal oxidases of the microaerophiles Campylobacter jejuni and Helicobacter pylori were analysed to identify structural elements that may be required for their unique energy metabolism. The gene clusters encoding NDH-1 in both C. jejuni and H. pylori lacked nuoE and nuoF, and in their place were genes encoding two unknown proteins. The NuoG subunit in these microaerophilic bacteria appeared to have an additional Fe-S cluster that is not present in NDH-1 from other organisms; but C. jejuni and H. pylori differed from each other in a cysteine-rich segment in this subunit, which is present in some but not all NDH-1. Both organisms lacked genes orthologous to those encoding NDH-2. The subunits of the bc1 complex of both bacteria were similar, and the Rieske Fe-S and cytochrome b subunits had significant similarity to those of Paracoccus denitrificans and Rhodobacter capsulatus, well-studied bacterial bc1 complexes. The composition of the terminal oxidases of C. jejuni and H. pylori was dif-
G. L. Mendz (✉) School of Biochemistry and Molecular Genetics, The University of New South Wales, Sydney, NSW 2052, Australia e-mail: [email protected], Tel.: +61-2-9385-2042, Fax: +61-2-9385-1483 M. A. Smith School of Microbiology and Immunology, The University of New South Wales, Sydney, NSW 2052, Australia M. Finel Department of Medical Chemistry, Institute of Biomedicine, P.O. Box 8 (Siltavuorenpenger 10), 00014 University of Helsinki, Helsinki, Finland V. Korolik School of Health Science, Griffith University, Gold Coast, Qld 4217, Australia
ferent; both bacteria had cytochrome cbb3 oxidases, but C. jejuni also contained a bd-type quinol oxidase. The primary structures of the major subunits of the cbb3-type (terminal) oxidase of C. jejuni and H. pylori indicated that they form a separate group within the cbb3 protein family. The implications of the results for the function of the enzymes and their adaptation to microaerophilic growth are discussed. Key words Respiratory chain · Microaerophiles · Campylobacter jejuni · Helicobacter pylori
Obligate microaerophiles are organisms with oxygen-dependent growth and which can use oxygen as a terminal acceptor, but they cannot grow under fully oxic conditions, or grow very poorly (Krieg and Hoffman 1986). Thus, oxygen is both necessary and deleterious for these microorganisms. Campylobacter jejuni and most species of the genus, as well as Helicobacter pylori and all the known species of the g
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