RT info:eu-repo/semantics/article
T1 Two nitrate/nitrite transporters are encoded within the mobilizable plasmid for nitrate respiration of Thermus thermophilus HB8
A1 Ramírez Arcos, Sandra
A1 Moreno Albiger, Renata
A1 Zafra Amorós, Olga
A1 Castán García, Pablo
A1 Valles Rapp, Cristina
A1 Berenguer Carlos, José
K1 Biologia molecular
K1 Bacterias
K1 Respiración
K1 Nitratos
K1 Nitrate respiration
K1 Thermophilic
K1 Thermus
AB Thermus thermophilus HB8 can grow anaerobically by using a membrane-bound nitrate reductase to catalyze the reduction of nitrate as a final electron acceptor in respiration. In contrast to other denitrifiers, the nitrite produced does not continue the reduction pathway but accumulates in the growth medium after its active extrusion from the cell. We describe the presence of two genes,narK1 and narK2, downstream of the nitrate reductase-encoding gene cluster (nar) that code for two homologues to the major facilitator superfamily of transporters. The sequences of NarK1 and NarK2 are 30% identical to each other, but whereas NarK1 clusters in an average-distance tree with putative nitrate transporters, NarK2 does so with putative nitrite exporters. To analyze whether this differential clustering was actually related to functional differences, we isolated derivatives with mutations of one or both genes. Analysis revealed that single mutations had minor effects on growth by nitrate respiration, whereas a double narK1 narK2 mutation abolished this capability. Further analysis allowed us to confirm that the double mutant is completely unable to excrete nitrite, while single mutants have a limitation in the excretion rates compared with the wild type. These data allow us to propose that both proteins are implicated in the transport of nitrate and nitrite, probably acting as nitrate/nitrite antiporters. The possible differential roles of these proteins in vivo are discussed.
PB American Society for Microbiology
SN 0021-9193
YR 2000
FD 2000
LK https://uvadoc.uva.es/handle/10324/53816
UL https://uvadoc.uva.es/handle/10324/53816
LA spa
NO Journal of Bacteriology, Vol. 182, Nº. 8, 2020, p. 2179-2183
NO Producción Científica
DS UVaDOC
RD 23-nov-2024