A thermostable K+-stimulated vacuolar-type pyrophosphatase from the hyperthermophilic bacterium Thermotoga maritima

Current evidence suggests the occurrence of two classes of vacuolar-type H-translocating inorganic pyrophosphatases (V-PPases): K+-insensitive protei ns, identified in eukaryotes, bacteria and archaea, and K+-stimulated V-PPa ses, identified to date only in eukaryotes, Here, we describe the functiona l characterization of a thermostable V-PPase from the anaerobic hyperthermo philic bacterium Thermotoga maritima by heterologous expression in Saccharo myces cerevisiae. The activity of this 71-kDa membrane-embedded polypeptide has a near obligate requirement for K+, like the plant V-PPase, and its th ermostability depends on the binding of Mg2+, Phylogenetic analysis of prot ein sequences consistently assigned the T, maritima V-PPase to the K+-sensi tive class of V-PPases so far only known for eukaryotes. The finding of a K +-stimulated V-PPase also in a member of a primitive eubacterial lineage st rongly supports an ancient evolutionary origin of this group of pyrophospha te-energized proton pumps, (C) 2001 Federation of European Biochemical Soci eties, Published by Elsevier Science B.V. All rights reserved.