The endosymbiont Amoebophilus asiaticus encodes an S-adenosylmethionine carrier that compensates for its missing methylation cycle

Author(s): Ilka Haferkamp, Thomas Penz, Melanie Geier, Michelle Ast, Tanja Mushak, Matthias Horn, Stephan Schmitz-Esser
Abstract: All organisms require S-adenosylmethionine (SAM) as a methyl group donor and cofactor for various biologically important processes. However, certain obligate intracellular parasitic bacteria and also the amoeba symbiont Amoebophilus asiaticus have lost the capacity to synthesize this cofactor and hence rely on its uptake from host cells. Genome analyses revealed that A. asiaticus encodes a putative SAM transporter. The corresponding protein was functionally characterized in Escherichia coli: import studies demonstrated that it is specific for SAM and S-adenosylhomocysteine (SAH), the end product of methylation. SAM transport activity was shown to be highly dependent on the presence of a membrane potential, and by targeted analyses, we obtained direct evidence for a proton-driven SAM/SAH antiport mechanism. Sequence analyses suggest that SAM carriers from Rickettsiales might operate in a similar way, in contrast to chlamydial SAM transporters. SAM/SAH antiport is of high physiological importance, as it allows for compensation for the missing methylation cycle. The identification of a SAM transporter in A. asiaticus belonging to the Bacteroidetes phylum demonstrates that SAM transport is more widely spread than previously assumed and occurs in bacteria belonging to three different phyla (Proteobacteria, Chlamydiae, and Bacteroidetes).
Organisation(s)
External organisation(s): Technische Universität Kaiserslautern
Journal: Journal of Bacteriology
Volume: 195
Pages: 3183-3192
No. of pages: 10
ISSN: 0021-9193
DOI: https://doi.org/10.1128/JB.00195-13
Publication date: 07-2013
Peer reviewed: Yes
Austrian Fields of Science 2012: 106022 Microbiology
Keywords
Portal url: https://ucrisportal.univie.ac.at/en/publications/cee64513-5f2e-466c-9665-b0f8b8c62264