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

In this study, the ATP synthase of was purified, characterized, and structurally compared to the respective enzymes of the other species, to shed light on energy conservation in this unique group of archaea. The crenarchaeal genus comprises three described species, i.e., and from hot marine sediments near Iceland and 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). is the best studied member of this genus, mainly because it is the only known host for the potentially parasitic archaeon 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 encodes nine subunits of an A-type ATP synthase, which we could identify in the purified complex. Although the maximal activity of the enzyme was measured around pH 6, the optimal stability of the AA complex seemed to be at pH 9. Interestingly, the soluble A subcomplexes of the different 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. The represent one of the major phyla within the 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 until now points to significant differences in stability, possibly caused by structural alterations. Furthermore, the study subject has a particular importance among crenarchaeotes, since it is the only known host of The energy metabolism in this system is still poorly understood, and our results can help elucidate the unique relationship between these two microbes.