Identification of the arginine/ornithine antiporter ArcD from Halobacterium salinarum

Abstract 

This paper identifies the first arginine/ornithine antiporter ArcD from the domain of archea. The functional role of ArcD is demonstrated by transport assays with radioactive labelled arginine, by its necessity to enable arginine fermentation under anaerobic growth conditions and by the consumption of arginine from the medium during growth. All three experimentally observables are severely disturbed when the deletion strain ΔArcD is used. The isolated protein is verified by mass spectrometry and reconstituted in vesicles. The proteoliposomes are attached to a membrane and capacitive currents are recorded which appear upon initiation of the transport process by change from arginine-free to arginine-containing buffer. This clearly demonstrates that the purified 34kD protein is the functional unit.

Abbreviations: DDM, dodecylmaltoside, MALDI-TOF, matrix assisted laser desorption ionisation-time of flight, ESI-MS/MS, electro spray ionization tandem mass spectrometry, TOM, strain of Halobacterium salinarum with two opsins missing, Nha, sodium hydrogen antiporter, SDS–PAGE, sodium dodecysulfate polyacrylamide gel electrophoresis, DIG, digoxygenine

Keywords: Arginine fermentation, Arginine transport, Membrane transport