Purification of a Crenarchaeal ATP Synthase in the Light of the Unique Bioenergetics of Ignicoccus Species

• Published in: Journal of Bacteriology
• Main Authors: Kreuter, Lydia J., Weinfurtner, Andrea, Ziegler, Alexander, Weigl, Julia, Hoffmann, Jan, Morgner, Nina, Müller, Volker, Huber, Harald
• Format: Text
• Language: English
• Published: American Society for Microbiology 2019
• Subjects: Research Article; Pacific; Iceland
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6416916/; http://www.ncbi.nlm.nih.gov/pubmed/30642991; https://doi.org/10.1128/JB.00510-18

In this study, the ATP synthase of Ignicoccus hospitalis was purified, characterized, and structurally compared to the respective enzymes of the other Ignicoccus species, to shed light on energy conservation in this unique group of archaea. The crenarchaeal genus Ignicoccus comprises three described species, i.e., I. hospitalis and Ignicoccus islandicus from hot marine sediments near Iceland and Ignicoccus pacificus from a hydrothermal vent system in the Pacific Ocean. This genus is unique among all archaea due to the unusual cell envelope, consisting of two membranes that enclose a large intermembrane compartment (IMC). I. hospitalis is the best studied member of this genus, mainly because it is the only known host for the potentially parasitic archaeon Nanoarchaeum equitans. I. hospitalis grows chemolithoautotrophically, and its sole energy-yielding reaction is the reduction of elemental sulfur with molecular hydrogen, forming large amounts of hydrogen sulfide. This reaction generates an electrochemical gradient, which is used by the ATP synthase, located in the outer cellular membrane, to generate ATP inside the IMC. The genome of I. hospitalis encodes nine subunits of an A-type ATP synthase, which we could identify in the purified complex. Although the maximal in vitro activity of the I. hospitalis enzyme was measured around pH 6, the optimal stability of the A(1)A(O) complex seemed to be at pH 9. Interestingly, the soluble A(1) subcomplexes of the different Ignicoccus species exhibited significant differences in their apparent molecular masses in native electrophoresis, although their behaviors in gel filtration and chromatography-mass spectrometry were very similar. IMPORTANCE The Crenarchaeota represent one of the major phyla within the Archaea domain. This study describes the successful purification of a crenarchaeal ATP synthase. To date, all information about A-type ATP synthases is from euryarchaeal enzymes. The fact that it has not been possible to purify this enzyme complex from a member of the ...