The Paracoccus denitrificans NarK-like nitrate and nitrite transporters; probing nitrate uptake and nitrate/nitrite exchange mechanisms
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Published version
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Author(s)
Type
Journal Article
Abstract
Nitrate and nitrite transport across biological mem
branes is often facilitated by protein
transporters that are members of the major facilita
tor superfamily.
Paracoccus
denitrificans
contains an unusual arrangement whereby two of the
se transporters,
NarK1 and NarK2, are fused into a single protein, N
arK, which delivers nitrate to the
respiratory nitrate reductase and transfers the pro
duct, nitrite, to the periplasm. Our
complementation studies, using a mutant lacking the
nitrate/proton symporter NasA
from the assimilatory nitrate reductase pathway, su
pport that NarK1 functions as a
nitrate/proton symporter while NarK2 is a nitrate/n
itrite antiporter. Through the same
experimental system, we find that
Escherichia coli
NarK and NarU can complement
deletions in both
narK
and
nasA
in
P. denitrificans
, suggesting that, while these proteins
are most likely nitrate/nitrite antiporters, they c
an also act in the net uptake of nitrate.
Finally, we argue that primary sequence analysis an
d structural modelling do not readily
explain why NasA, NarK1 and NarK2, as well as other
transporters from this protein
family, have such different functions, ranging from
net nitrate uptake to nitrate/nitrite
exchange.
branes is often facilitated by protein
transporters that are members of the major facilita
tor superfamily.
Paracoccus
denitrificans
contains an unusual arrangement whereby two of the
se transporters,
NarK1 and NarK2, are fused into a single protein, N
arK, which delivers nitrate to the
respiratory nitrate reductase and transfers the pro
duct, nitrite, to the periplasm. Our
complementation studies, using a mutant lacking the
nitrate/proton symporter NasA
from the assimilatory nitrate reductase pathway, su
pport that NarK1 functions as a
nitrate/proton symporter while NarK2 is a nitrate/n
itrite antiporter. Through the same
experimental system, we find that
Escherichia coli
NarK and NarU can complement
deletions in both
narK
and
nasA
in
P. denitrificans
, suggesting that, while these proteins
are most likely nitrate/nitrite antiporters, they c
an also act in the net uptake of nitrate.
Finally, we argue that primary sequence analysis an
d structural modelling do not readily
explain why NasA, NarK1 and NarK2, as well as other
transporters from this protein
family, have such different functions, ranging from
net nitrate uptake to nitrate/nitrite
exchange.
Date Issued
2016-10-27
Date Acceptance
2016-09-29
Citation
Molecular Microbiology, 2016, 103 (1), pp.117-133
ISSN
1365-2958
Publisher
Wiley
Start Page
117
End Page
133
Journal / Book Title
Molecular Microbiology
Volume
103
Issue
1
Copyright Statement
© 2016 The Authors. Molecular Microbiology Published by John Wiley & Sons Ltd
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Sponsor
Medical Research Council
Grant Number
MR/M009505/1
Subjects
06 Biological Sciences
11 Medical And Health Sciences
07 Agricultural And Veterinary Sciences
Microbiology
Publication Status
Published