The electron transport system of Alcaligenes eutrophus H16 |
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Authors: | Ralf Kömen Davide Zannoni W John Ingledew Karin Schmidt |
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Institution: | (1) Institut für Mikrobiologie der Georg-August0Universität, Grisebachstrasse 8, W-3400 Göttingen, Federal Republic of Germany;(2) Department of Biology, University of Bologna, I-40126 Bologna, Italy;(3) Department of Biochemistry and Microbiology, St. Andrews Univesity, St. Andrews, UK |
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Abstract: | The electron transport system of autotrophically grown Alcaligenes eutrophus H16 has been investigated by spectroscopic and thermodynamic approaches. The results have been interpreted as evidence that isolated membranes contain a branched respiratory chain composed of three c-type haems (E
m,7=+160 mV, + 170 mV, and + 335 mV), five b-type haems (E
m,7=+ 5 mV, + 75 mV, + 205 mV, + 300 mV, and + 405 mV), two (possibly three) a-type haems E
m,7= + 255 mV, + 350 mV, (+ 420 mV)], and nne d-type haem. EPR-analysis of the signals at g=1.93, g=2.02, and g=1.90 revealed the presence of iron-sulphur centres diagnostic of complexes I (NADH dehydrogenase), II (succinate dehydrogenase), and III (ubiquinol/cytochrome c oxidoreductase). The low potential b haems (+ 5 mV and + 75 mV) plus the Rieske protein (g=1.90, E
m,7=+ 280 mV), thought to be part of an orthodox bc
1 complex, were present in low amounts as compared to their counterparts in membranes from Paracoccus denitrificans.CO-difference spectra in the presence of either succinate, NADH, hydrogen, ascorbate/TMPD, and/or dithionite as reductants, suggested the existance of four different oxidases composed by bo-, cb-, a-, and d-type haems.It is concluded that in contrast to other chemolithotrophes, e.g. P. denitrificans, autotrophic growth of Alcaligenes eutrophus utilizes a respiratory system in which the bc
1 complex containing pathway is only partially involved in electron transport.Abbreviations Cytochrome c-551, number
wavelength in nm
- Cytochrome c
270, number
mid-point potential in mV
-
E
m,7
mid-point potential of an oxidation-reduction couple at pH 7.0
- KP
buffer, potassium phosphate-buffer
- OD
optical density at 436 nm, 1 cm light path
- TMPD
N,N,N ,N -tetramethyl-p-phenylenediamine |
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Keywords: | Alcaligenes eutrophus H16 Paracoccus denitrificans Electron transport system Cytochrome composition Ubiquinol-cytochrome c oxidoreductase Terminal oxidases |
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