Peroxisomal localization of sulfite oxidase separates it from chloroplast-based sulfur assimilation.
Recently, we isolated the sulfite oxidase (SO) gene from Arabidopsis thaliana and characterized the purified SO protein. The purpose of the present study was to determine the subcellular localization of this novel plant enzyme. Immunogold electron-microscopic analysis showed the gold labels nearly exclusively in the peroxisomes. To verify this finding, green fluorescent protein was fused to full-length plant SO including the putative peroxisomal targeting signal 1 (PTS1) 'SNL' and expressed in tobacco leaves. Our results showed a punctate fluorescence pattern resembling that of peroxisomes. Co-labelling with MitoTracker-Red excluded that the observed fluorescence was due to mitochondrial sorting. By investigation of deleted or mutated PTS1, no functional peroxisomal targeting signal 2 (PTS2) could be detected in plant SO. This conclusion is supported by expression studies in Pichia pastoris mutants with defined defects either in PTS1- or PTS2-mediated peroxisomal import.
Nowak
Katharina
K
Department of Plant Biology, Technical University of Braunschweig, Humboldtstrasse 1, D-38106 Braunschweig, Germany.
Luniak
Nora
N
Witt
Christina
C
Wüstefeld
Yvonne
Y
Wachter
Andreas
A
Mendel
Ralf R
RR
Hänsch
Robert
R
D017360:Arabidopsis / Q000201:enzymology* / Q000648:ultrastructure; D002736:Chloroplasts / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D009930:Organic Chemicals; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000378:metabolism*; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism* / Q000648:ultrastructure; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*; D014026:Nicotiana / Q000201:enzymology / Q000648:ultrastructure
D005456:Fluorescent Dyes; D009930:Organic Chemicals; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; C485192:green fluorescent protein, Aequorea victoria; C107472:red dye CMXRos; D049452:Green Fluorescent Proteins; D013455:Sulfur; D050862:Oxidoreductases Acting on Sulfur Group Donors