-
[show abstract]
[hide abstract]
ABSTRACT: Iron-sulfur (Fe-S) clusters are ubiquitous prosthetic groups required to sustain fundamental life processes. The assembly of Fe-S clusters and insertion into polypeptides in vivo has recently become an area of intense research. Many of the genes involved are conserved in bacteria, fungi, animals and plants. Plant cells can carry out both photosynthesis and respiration - two processes that require significant amounts of Fe-S proteins. Recent findings now suggest that both plastids and mitochondria are capable of assembling Fe-S proteins using assembly machineries that differ in biochemical properties, genetic make-up and evolutionary origin.
Trends in Plant Science 08/2005; 10(7):324-31. · 11.05 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Isu are scaffold proteins involved in iron-sulfur cluster biogenesis and playing a key role in yeast mitochondria and Escherichia coli. In this work, we have characterized the Arabidopsis thaliana Isu gene family. AtIsu1,2,3 genes encode polypeptides closely related to their bacterial and eukaryotic counterparts. AtIsu expression in a Saccharomyces cerevisiae Deltaisu1Deltanfu1 thermosensitive mutant led to the growth restoration of this strain at 37 degrees C. Using Isu-GFP fusions expressed in leaf protoplasts and immunodetection in organelle extracts, we have shown that Arabidopsis Isu proteins are located only into mitochondria, supporting the existence of an Isu-independent Fe-S assembly machinery in plant plastids.
FEBS Letters 04/2005; 579(9):1930-4. · 3.54 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Nfu proteins are candidates to act as scaffold protein in vivo for iron-sulphur cluster biogenesis. In this work, Nfu2 protein function in the chloroplast was investigated in vivo using T-DNA insertion lines disrupted in AtNfu2 gene. Both alleles characterized presented the same dwarf phenotype due to photosynthetic and metabolic limitations. Nfu2 cDNA expression in nfu2.1 mutant rescued this phenotype. Photosynthesis study of these mutants revealed an altered photosystem I (PSI) activity together with a decrease in PSI amount confirmed by immunodetection experiments, and leading to an over reduction of the plastoquinol pool. Decrease of plastid 4Fe-4S sulphite reductase activity correlates with PSI amount decrease and supports an alteration of 4Fe-4S cluster biogenesis in nfu2 chloroplasts. The decrease of electron flow from the PSI is combined with a decrease in ferredoxin amount in nfu2 mutants. Our results are therefore in favour of a requirement of Nfu2 protein for 4Fe-4S and 2Fe-2S ferredoxin cluster assembly, conferring to this protein an important function for plant growth and photosynthesis as demonstrated by nfu2 mutant phenotype. As glutamate synthase and Rieske Fe-S proteins are not affected in nfu2 mutants, these data indicate that different pathways are involved in Fe-S biogenesis in Arabidopsis chloroplasts.
The Plant Journal 11/2004; 40(1):101-11. · 6.16 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Recent results are in favour of a role for NFU-like proteins in Fe-S cluster biogenesis. These polypeptides share a conserved CXXC motif in their NFU domain. In the present study, we have characterized Arabidopsis thaliana NFU1-5 genes. AtNFU proteins are separated into two classes. NFU4 and NFU5 are part of the mitochondrial type, presenting a structural organization similar to Saccharomyces cerevisiae Nfu1p. These proteins complement a Delta isu1 Delta nfu1 yeast mutant and NFU4 mitochondrial localization was confirmed by green fluorescent protein fusion analysis. AtNFU1-3 represent a new class of NFU proteins, unique to plants. These polypeptides are made of two NFU domains, the second having lost its CXXC motif. AtNFU1-3 proteins are more related to Synechocystis PCC6803 NFU-like proteins and are localized to plastids when fused with the green fluorescent protein. NFU2 and/or NFU3 were detected in leaf chloroplasts by immunoblotting. NFU1 and NFU2 are functional NFU capable of restoring the growth of a Delta isu1 Delta nfu1 yeast mutant, when addressed to yeast mitochondria. Furthermore, NFU2 recombinant protein is capable of binding a labile 2Fe-2S cluster in vitro. These results demonstrate the presence of distinct NFU proteins in Arabidopsis mitochondria and plastids. Such results suggest the existence of two different Fe-S assembly machineries in plant cells.
Biochemical Journal 06/2003; 371(Pt 3):823-30. · 4.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: NifS-like proteins are cysteine desulphurases required for the mobilization of sulphur from cysteine. They are present in all organisms, where they are involved in iron-sulphur (Fe-S) cluster biosynthesis. In eukaryotes, these enzymes are present in mitochondria, which are the major site for Fe-S cluster assembly. The genome of the model plant Arabidopsis thaliana contains two putative NifS-like proteins. A cDNA corresponding to one of them was cloned by reverse-transcription PCR, and named AtNFS2. The corresponding transcript is expressed in many plant tissues. It encodes a protein highly related (75% similarity) to the slr0077-gene product from Synechocystis PCC 6803, and is predicted to be targeted to plastids. Indeed, a chimaeric AtNFS2-GFP fusion protein, containing one-third of AtNFS2 from its N-terminal end, was addressed to chloroplasts. Overproduction in Escherichia coli and purification of recombinant AtNFS2 protein enabled one to demonstrate that it bears a pyridoxal 5'-phosphate-dependent cysteine desulphurase activity in vitro, thus being the first NifS homologue characterized to date in plants. The putative physiological functions of this gene are discussed, including the attractive hypothesis of a possible role in Fe-S cluster assembly in plastids.
Biochemical Journal 10/2002; 366(Pt 2):557-64. · 4.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Transformation of yeast cells with a maize cDNA ZmPAA, encoding a 20S proteasome alpha-subunit, conferred resistance to nickel, cadmium and cobalt. This resistance is not linked to a modification of the intracellular nickel content, as no accumulation of nickel was measured between yeast cells transformed with a void vector or the ZmPAA cDNA. The abundance of the ZmPAA mRNA was increased in the shoots of maize plants upon nickel treatment. These results suggest that the proteasome might be involved in nickel resistance by scavenging metal oxidized proteins both in plants and yeast.
Gene 07/2002; 293(1-2):199-204. · 2.34 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Transformation of yeast cells with a maize cDNA ZmPAA, encoding a 20S proteasome α-subunit, conferred resistance to nickel, cadmium and cobalt. This resistance is not linked to a modification of the intracellular nickel content, as no accumulation of nickel was measured between yeast cells transformed with a void vector or the ZmPAA cDNA. The abundance of the ZmPAA mRNA was increased in the shoots of maize plants upon nickel treatment. These results suggest that the proteasome might be involved in nickel resistance by scavenging metal oxidized proteins both in plants and yeast.
Gene.
