Reference "Molecular identification and functional characterization of Arabidopsis thaliana mitochondrial and chloroplastic NAD+ carrier proteins"

Reference ID

54979

Title

Molecular identification and functional characterization of Arabidopsis thaliana mitochondrial and chloroplastic NAD+ carrier proteins

Source

J Biol Chem, 2009, vol. 284, pp. 31249-31259

Authors (14)

Palmieri-F	Rieder-B	Ventrella-A	Blanco-E
Do-P-T	Nunes-Nesi-A	Trauth-A-U	Fiermonte-G
Tjaden-J	Agrimi-G	Kirchberger-S	Paradies-E
Fernie-A-R	Neuhaus-H-E

Abstract

The Arabidopsis thaliana L. genome contains 58 membrane proteins belonging to
the mitochondrial carrier family. Two mitochondrial carrier family members, here
named AtNDT1 and AtNDT2, exhibit high structural similarities to the
mitochondrial nicotinamide adenine dinucleotide (NAD(+)) carrier ScNDT1 from
bakers' yeast. Expression of AtNDT1 or AtNDT2 restores mitochondrial NAD(+)
transport activity in a yeast mutant lacking ScNDT. Localization studies with
green fluorescent protein fusion proteins provided evidence that AtNDT1 resides
in chloroplasts, whereas only AtNDT2 locates to mitochondria. Heterologous
expression in Escherichia coli followed by purification, reconstitution in
proteoliposomes, and uptake experiments revealed that both carriers exhibit a
submillimolar affinity for NAD(+) and transport this compound in a counter-
exchange mode. Among various substrates ADP and AMP are the most efficient counter-
exchange substrates for NAD(+). Atndt1- and Atndt2-promoter-GUS plants
demonstrate that both genes are strongly expressed in developing tissues and in
particular in highly metabolically active cells. The presence of both carriers
is discussed with respect to the subcellular localization of de novo NAD(+)
biosynthesis in plants and with respect to both the NAD(+)-dependent metabolic
pathways and the redox balance of chloroplasts and mitochondria.