Three multihaem cytochromes c from the hyperthermophilic archaeon Ignicoccus hospitalis: purification, properties and localization.
Three different multihaem cytochromes c were purified from cell extracts of the hyperthermophilic archaeon Ignicoccus hospitalis. One tetrahaem cytochrome, locus tag designation Igni_0530, was purified from membrane fractions together with the iron-sulfur protein Igni_0529. Two octahaem cytochromes, Igni_0955 and Igni_1359, were purified from soluble fractions but were also present in the membrane fraction. N-terminal sequencing showed that three of the four proteins had their signal peptides cleaved off, while results were ambiguous for Igni_0955. In contrast, mass spectrometry of Igni_0955 and Igni_1359 resulted in single mass peaks including the signal sequences and eight haems per subunit and so both forms might be present in the cell. Igni_0955 and Igni_1359 belong to the hydroxylamine dehydrogenase (HAO) family (29 % mutual identity). HAO or reductase activities with inorganic sulfur compounds were not detected. Igni_0955 was reduced by enriched I. hospitalis hydrogenase at a specific activity of 243 nmol min(-1) (mg hydrogenase)(-1) while activity was non-existent for Igni_0530 and low for Igni_1359. Immuno-electron microscopy of ultra-thin sections showed that Igni_0955 and Igni_1359 are located in both I. hospitalis membranes and also in the intermembrane compartment. We concluded that these cytochromes might function as electron shuttles between the hydrogenase in the outer cellular membrane and cellular reductases, whereas Igni_0530 might be part of the sulfur-reducing mechanism.
Technische Universität Darmstadt, Microbiology - Sulfur Biochemistry and Microbial Bioenergetics, Darmstadt, Germany.
Bastian
B
Naß
Technische Universität Darmstadt, Microbiology - Sulfur Biochemistry and Microbial Bioenergetics, Darmstadt, Germany.
Uwe
U
Pöll
Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany.
Julian David
JD
Langer
Lehrstuhl für Mikrobiologie, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
Lydia
L
Kreuter
Lehrstuhl für Mikrobiologie, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
Ulf
U
Küper
Zentrum für Elektronenmikroskopie, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
Jennifer
J
Flechsler
Zentrum für Elektronenmikroskopie, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
Thomas
T
Heimerl
Zentrum für Elektronenmikroskopie, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
Reinhard
R
Rachel
Lehrstuhl für Mikrobiologie, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
Harald
H
Huber
Technische Universität Darmstadt, Microbiology - Sulfur Biochemistry and Microbial Bioenergetics, Darmstadt, Germany.
Arnulf
A
Kletzin
D002462:Cell Membrane / Q000737:chemistry / Q000201:enzymology; D045304:Cytochromes c / Q000302:isolation & purification* / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry / Q000201:enzymology; D019620:Desulfurococcaceae / Q000737:chemistry / Q000201:enzymology*; D013058:Mass Spectrometry; D016253:Microscopy, Immunoelectron; D020539:Sequence Analysis, Protein
D045304:Cytochromes c