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Bioenergetics and the role of soluble cytochromes C for alkaline adaptation in gram-negative alkaliphilic Pseudomonas.

ABSTRACT: Very few studies have been conducted on alkaline adaptation of Gram-negative alkaliphiles. The reversed difference of H(+) concentration across the membrane will make energy production considerably difficult for Gram-negative as well as Gram-positive bacteria. Cells of the alkaliphilic Gram-negative bacterium Pseudomonas alcaliphila AL15-21(T) grown at pH 10 under low-aeration intensity have a soluble cytochrome c content that is 3.6-fold higher than that of the cells grown at pH 7 under high-aeration intensity. Cytochrome c-552 content was higher (64% in all soluble cytochromes c) than those of cytochrome c-554 and cytochrome c-551. In the cytochrome c-552-dificient mutant grown at pH 10 under low-aeration intensity showed a marked decrease in ? max? [h(-1)] (40%) and maximum cell turbidity (25%) relative to those of the wild type. Considering the high electron-retaining abilities of the three soluble cytochromes c, the deteriorations in the growth of the cytochrome c-552-deficient mutant could be caused by the soluble cytochromes c acting as electron storages in the periplasmic space of the bacterium. These electron-retaining cytochromes c may play a role as electron and H(+) condenser, which facilitate terminal oxidation at high pH under air-limited conditions, which is difficult to respire owing to less oxygen and less H(+).

SUBMITTER: Matsuno T

PROVIDER: S-EPMC4332470 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Bioenergetics and the role of soluble cytochromes C for alkaline adaptation in gram-negative alkaliphilic Pseudomonas.

Matsuno T T Yumoto I I

BioMed research international 20150202

Very few studies have been conducted on alkaline adaptation of Gram-negative alkaliphiles. The reversed difference of H(+) concentration across the membrane will make energy production considerably difficult for Gram-negative as well as Gram-positive bacteria. Cells of the alkaliphilic Gram-negative bacterium Pseudomonas alcaliphila AL15-21(T) grown at pH 10 under low-aeration intensity have a soluble cytochrome c content that is 3.6-fold higher than that of the cells grown at pH 7 under high-ae ...[more]

PMID: 25705691

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Project description:Significant progress has been made in isolating novel alkaline ?-mannanases, however, there is a paucity of information concerning the structural basis for alkaline tolerance displayed by these ?-mannanases. We report the catalytic domain structure of an industrially important ?-mannanase from the alkaliphilic Bacillus sp. N16-5 (BSP165 MAN) at a resolution of 1.6 Å. This enzyme, classified into subfamily 8 in glycosyl hydrolase family 5 (GH5), has a pH optimum of enzymatic activity at pH 9.5 and folds into a classic (?/?)(8)-barrel. In order to gain insight into molecular features for alkaline adaptation, we compared BSP165 MAN with previously reported GH5 ?-mannanases. It was revealed that BSP165 MAN and other subfamily 8 ?-mannanases have significantly increased hydrophobic and Arg residues content and decreased polar residues, comparing to ?-mannanases of subfamily 7 or 10 in GH5 which display optimum activities at lower pH. Further, extensive structural comparisons show alkaline ?-mannanases possess a set of distinctive features. Position and length of some helices, strands and loops of the TIM barrel structures are changed, which contributes, to a certain degree, to the distinctly different shaped (?/?)(8)-barrels, thus affecting the catalytic environment of these enzymes. The number of negatively charged residues is increased on the molecular surface, and fewer polar residues are exposed to the solvent. Two amino acid substitutions in the vicinity of the acid/base catalyst were proposed to be possibly responsible for the variation in pH optimum of these homologous enzymes in subfamily 8 of GH5, identified by sequence homology analysis and pK(a) calculations of the active site residues. Mutational analysis has proved that Gln91 and Glu226 are important for BSP165 MAN to function at high pH. These findings are proposed to be possible factors implicated in the alkaline adaptation of GH5 ?-mannanases and will help to further understanding of alkaline adaptation mechanism.

Dataset Information

Bioenergetics and the role of soluble cytochromes C for alkaline adaptation in gram-negative alkaliphilic Pseudomonas.

Publications

Bioenergetics and the role of soluble cytochromes C for alkaline adaptation in gram-negative alkaliphilic Pseudomonas.

Similar Datasets

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