title: AVP2, a sequence-divergent, K(+)-insensitive H(+)-translocating inorganic pyrophosphatase from Arabidopsis.
abstract: Plant vacuolar H(+)-translocating inorganic pyrophosphatases (V-PPases; EC 3.6.1.1) have been considered to constitute a family of functionally and structurally monotonous intrinsic membrane proteins. Typified by AVP1 (V. Sarafian, Y. Kim, R.J. Poole, P.A. Rea [1992] Proc Natl Acad Sci USA 89: 1775-1779) from Arabidopsis, all characterized plant V-PPases share greater than 84% sequence identity and catalyze K(+)-stimulated H(+) translocation. Here we describe the molecular and biochemical characterization of AVP2 (accession no. AF182813), a sequence-divergent (36% identical) K(+)-insensitive, Ca(2+)-hypersensitive V-PPase active in both inorganic pyrophosphate hydrolysis and H(+) translocation. The differences between AVP2 and AVP1 provide the first indication that plant V-PPases from the same organism fall into two distinct categories. Phylogenetic analyses of these and other V-PPase sequences extend this principle by showing that AVP2, rather than being an isoform of AVP1, is but one representative of a novel category of AVP2-like (type II) V-PPases that coexist with AVP1-like (type I) V-PPases not only in plants, but also in apicomplexan protists such as the malarial parasite Plasmodium falciparum.
authors.affiliation: Plant Science Institute, Department of Biology, University of Pennsylvania, Philadelphia 19104-6018, USA.
authors.forename: Y M
authors.initials: YM
authors.lastname: Drozdowicz
authors.forename: J C
authors.initials: JC
authors.lastname: Kissinger
authors.forename: P A
authors.initials: PA
authors.lastname: Rea
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D017136:Ion Transport; D008969:Molecular Sequence Data; D010802:Phylogeny; D011188:Potassium / Q000378:metabolism*; D011755:Pyrophosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D011755:Pyrophosphatases; D011188:Potassium