2.A.1.8.17
Nitrate/nitrite transporter, NarK2, of 468 aas and 12 TMSs. The narK1 and narK2 genes are located in an operon, narK1K2GHJI, with the structural genes for the nitrate reductase complex.  Utilizing an isogenic narK1 mutant, a narK2 mutant, and a narK1K2 double mutant, Sharma et al. 2006 explored the effect on growth under denitrifying conditions. While the ΔnarK1::Gm mutant was only slightly affected, but both the ΔnarK2::Gm and double mutants exhibited poor nitrate-dependent, anaerobic growth although all three strains had wild-type levels of nitrate reductase activity. Nitrate uptake measurements showed that NarK2 has most of the activity.  E. coli narK rescued both mutants.