title: Rhodospirillum rubrum has a family I pyrophosphatase: purification, cloning, and sequencing.
abstract: The cytoplasmic pyrophosphatase of the photosynthetic bacterium Rhodospirillum rubrum was purified to electrophoretic homogeneity. The enzyme is a homohexamer of 20-kDa monomers. The gene was cloned and sequenced. Alignment of the deduced 179-amino-acid protein with known bacterial pyrophosphatases revealed conservation of all residues in the active site. Attempts to obtain an insertion mutant of the cytoplasmic pyrophosphatase gene did not yield any cell completely devoid of cytoplasmic pyrophosphatase activity. The mutants obtained showed 50% of the enzymatic activity and grew in twice the generation time of wild-type cells. This suggests that the membrane-bound pyrophosphatase of Rsp. rubrum is not sufficient for a normal growth rate, whereas the cytoplasmic enzyme is essential for growth. The characteristics of the gene and the encoded protein fit those of prokaryotic family I pyrophosphatases.
authors.affiliation: Departamento de Bioquímica, Facultad de Medicina, Edificio D 2 masculine Piso Universidad Nacional Autónoma de México. 04510, D.F. Mexico, México. iromero@ifisiol.unam.mx
authors.forename: Irma
authors.initials: I
authors.lastname: Romero
authors.forename: Rodolfo
authors.initials: R
authors.lastname: García-Contreras
authors.forename: Heliodoro
authors.initials: H
authors.lastname: Celis
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D009154:Mutation; D011755:Pyrophosphatases / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D012247:Rhodospirillum rubrum / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D011755:Pyrophosphatases