Unbound MEDLINE

AMP-forming acetyl coenzyme A synthetase in the outermost membrane of the hyperthermophilic crenarchaeon Ignicoccus hospitalis.

Abstract

Ignicoccus hospitalis, a hyperthermophilic, chemolithoautotrophic crenarchaeon was found to possess a new CO(2) fixation pathway, the dicarboxylate/4-hydroxybutyrate cycle. The primary acceptor molecule for this pathway is acetyl coenzyme A (acetyl-CoA), which is regenerated in the cycle via the characteristic intermediate 4-hydroxybutyrate. In the presence of acetate, acetyl-CoA can alternatively be formed in a one-step mechanism via an AMP-forming acetyl-CoA synthetase (ACS). This enzyme was identified after membrane preparation by two-dimensional native PAGE/SDS-PAGE, followed by matrix-assisted laser desorption ionization-time of flight tandem mass spectrometry and N-terminal sequencing. The ACS of I. hospitalis exhibits a molecular mass of ∼690 kDa with a monomeric molecular mass of 77 kDa. Activity tests on isolated membranes and bioinformatic analyses indicated that the ACS is a constitutive membrane-associated (but not an integral) protein complex. Unexpectedly, immunolabeling on cells of I. hospitalis and other described Ignicoccus species revealed that the ACS is localized at the outermost membrane. This perfectly coincides with recent results that the ATP synthase and the H(2):sulfur oxidoreductase complexes are also located in the outermost membrane of I. hospitalis. These results imply that the intermembrane compartment of I. hospitalis is not only the site of ATP synthesis but may also be involved in the primary steps of CO(2) fixation.

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  • Authors

    Mayer F, Küper U, Meyer C, Daxer S, Müller V, Rachel R, Huber H

    Source

    Journal of bacteriology 194:6 2012 Mar pg 1572-81

    MeSH

    Acetate-CoA Ligase
    Adenosine Monophosphate
    Archaeal Proteins
    Desulfurococcaceae
    Electrophoresis, Gel, Two-Dimensional
    Membrane Proteins
    Microscopy
    Models, Biological
    Molecular Weight
    Protein Multimerization
    Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    22247508