TU Darmstadt / ULB / TUbiblio

An extracellular tetrathionate hydrolase from the thermoacidophilic archaeon Acidianus ambivalens with an activity optimum at pH 1

Protze, Jonas and Müller, Fabian and Lauber, Karin and Naß, Bastian and Mentele, Reinhard and Lottspeich, Friedrich and Kletzin, Arnulf (2011):
An extracellular tetrathionate hydrolase from the thermoacidophilic archaeon Acidianus ambivalens with an activity optimum at pH 1.
In: Frontiers in microbial physiology and metabolism, 2, (68), [Online-Edition: http://www.frontiersinneuroscience.org/Microbial_Physiology_...],
[Article]

Abstract

Background: The thermoacidophilic and chemolithotrophic archaeon Acidianus ambivalens is routinely grown with sulfur and CO2-enriched air. We had described a membrane-bound, tetrathionate (TT) forming thiosulfate:quinone oxidoreductase. Here we describe the first TT hydrolase (TTH) from Archaea. Results: A. ambivalens cells grown aerobically with TT as sole sulfur source showed doubling times of 9 h and final cell densities of up to 8 × 108/ml. TTH activity (≈0.28 U/mg protein) was found in cell-free extracts of TT-grown but not of sulfur-grown cells. Differential fractionation of freshly harvested cells involving a pH shock showed that about 92% of the TTH activity was located in the pseudo-periplasmic fraction associated with the surface layer, while 7.3% and 0.3% were present in the soluble and membrane fractions, respectively. The enzyme was enriched 54-fold from the cytoplasmic fraction and 2.1-fold from the pseudo-periplasmic fraction. The molecular mass of the single subunit was 54 kDa. The optimal activity was at or above 95°C at pH 1. Neither PQQ nor divalent cations had a significant effect on activity. The gene (tth1) was identified following N-terminal sequencing of the protein. Northern hybridization showed that tth1 was transcribed in TT-grown cells in contrast to a second paralogous tth2 gene. The deduced amino acid sequences showed similarity to the TTH from Acidithiobacillus and other proteins from the PQQ dehydrogenase superfamily. It displayed a β-propeller structure when being modeled, however, important residues from the PQQ-binding site were absent. Conclusion: The soluble, extracellular, and acidophilic TTH identified in TT-grown A. ambivalens cells is essential for TT metabolism during growth but not for the downstream processing of the TQO reaction products in S°-grown cells. The liberation of TTH by pH shock from otherwise intact cells strongly supports the pseudo-periplasm hypothesis of the S-layer of Archaea.

Item Type: Article
Erschienen: 2011
Creators: Protze, Jonas and Müller, Fabian and Lauber, Karin and Naß, Bastian and Mentele, Reinhard and Lottspeich, Friedrich and Kletzin, Arnulf
Title: An extracellular tetrathionate hydrolase from the thermoacidophilic archaeon Acidianus ambivalens with an activity optimum at pH 1
Language: English
Abstract:

Background: The thermoacidophilic and chemolithotrophic archaeon Acidianus ambivalens is routinely grown with sulfur and CO2-enriched air. We had described a membrane-bound, tetrathionate (TT) forming thiosulfate:quinone oxidoreductase. Here we describe the first TT hydrolase (TTH) from Archaea. Results: A. ambivalens cells grown aerobically with TT as sole sulfur source showed doubling times of 9 h and final cell densities of up to 8 × 108/ml. TTH activity (≈0.28 U/mg protein) was found in cell-free extracts of TT-grown but not of sulfur-grown cells. Differential fractionation of freshly harvested cells involving a pH shock showed that about 92% of the TTH activity was located in the pseudo-periplasmic fraction associated with the surface layer, while 7.3% and 0.3% were present in the soluble and membrane fractions, respectively. The enzyme was enriched 54-fold from the cytoplasmic fraction and 2.1-fold from the pseudo-periplasmic fraction. The molecular mass of the single subunit was 54 kDa. The optimal activity was at or above 95°C at pH 1. Neither PQQ nor divalent cations had a significant effect on activity. The gene (tth1) was identified following N-terminal sequencing of the protein. Northern hybridization showed that tth1 was transcribed in TT-grown cells in contrast to a second paralogous tth2 gene. The deduced amino acid sequences showed similarity to the TTH from Acidithiobacillus and other proteins from the PQQ dehydrogenase superfamily. It displayed a β-propeller structure when being modeled, however, important residues from the PQQ-binding site were absent. Conclusion: The soluble, extracellular, and acidophilic TTH identified in TT-grown A. ambivalens cells is essential for TT metabolism during growth but not for the downstream processing of the TQO reaction products in S°-grown cells. The liberation of TTH by pH shock from otherwise intact cells strongly supports the pseudo-periplasm hypothesis of the S-layer of Archaea.

Journal or Publication Title: Frontiers in microbial physiology and metabolism
Volume: 2
Number: 68
Divisions: 10 Department of Biology > Sulfur Biochemistry and Microbial Bioenergetics
?? fb10_mikrobiologie ??
10 Department of Biology
Date Deposited: 25 May 2011 08:38
Official URL: http://www.frontiersinneuroscience.org/Microbial_Physiology_...
Identification Number: doi:10.3389/fmicb.2011.00068
Export:
Suche nach Titel in: TUfind oder in Google

Optionen (nur für Redakteure)

View Item View Item