Sinorhizobium meliloti Nia is a P(1B-5)-ATPase expressed in the nodule during plant symbiosis and is involved in Ni and Fe transport.
The P1B-ATPases are a ubiquitous family of metal transporters. These transporters are classified into subfamilies on the basis of substrate specificity, which is conferred by conserved amino acids in the last three transmembrane domains. Five subfamilies have been identified to date, and representative members of four (P1B-1 to P1B-4) have been studied. The fifth family (P1B-5), of which some members contain a C-terminal hemerythrin (Hr) domain, is less well characterized. The S. meliloti Sma1163 gene encodes for a P1B-5-ATPase, denoted Nia (Nickel-iron ATPase), that is induced by exogenous Fe(2+) and Ni(2+). The nia mutant accumulates nickel and iron, suggesting a possible role in detoxification of these two elements under free-living conditions, as well as in symbiosis, when the highest expression levels are measured. This function is supported by an inhibitory effect of Fe(2+) and Ni(2+) on the pNPPase activity, and by the ability of Nia to bind Fe(2+) in the transmembrane domain. Optical and X-ray absorption spectroscopic studies of the isolated Hr domain confirm the presence of a dinuclear iron center and suggest that this domain might function as an iron sensor.
Departments of Molecular Biosciences and of Chemistry. Northwestern University, Evanston, Illinois, USA. amyr@northwestern.edu.
Eliza L
EL
Zielazinski
Centro de Biotecnología y Genómica de Plantas (CBGP), Universidad Politécnica de Madrid, Campus de Montegancedo, Pozuelo de Alarcón, Madrid, Spain.
Manuel
M
González-Guerrero
Department of Biochemistry and Molecular Biology and the Cardiovascular Research Institute, Wayne State University, School of Medicine, Detroit, Michigan, USA.
Poorna
P
Subramanian
Department of Biochemistry and Molecular Biology and the Cardiovascular Research Institute, Wayne State University, School of Medicine, Detroit, Michigan, USA.
Timothy L
TL
Stemmler
Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts, USA. arguello@wpi.edu.
José M
JM
Argüello
Departments of Molecular Biosciences and of Chemistry. Northwestern University, Evanston, Illinois, USA. amyr@northwestern.edu.
Amy C
AC
Rosenzweig
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D015870:Gene Expression; D007501:Iron / Q000378:metabolism*; D008958:Models, Molecular; D009532:Nickel / Q000378:metabolism*; D018521:Plant Physiological Phenomena; D016962:Sinorhizobium meliloti / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D013559:Symbiosis
D009532:Nickel; D007501:Iron; D000251:Adenosine Triphosphatases