Dual targeting and function of a protease in mitochondria and chloroplasts.
Here we show, using the green fluorescent protein (GFP) fusion system, that an Arabidopsis thaliana zinc-metalloprotease (AtZn-MP) is targeted to both mitochondria and chloroplasts. A deletion mutant lacking the amino-terminal 28 residues, with translation initiation at the second methionine residue, was imported into chloroplasts only. However, a mutated form of the full-length targeting peptide, in which the second methionine residue is changed to leucine, was imported to both organelles. No GFP fluorescence was detected when a frame-shift mutation was introduced between the first and second ATG codons of the Zn-MP-GFP construct, suggesting no alternative translational initiation. Our results show that the dual targeting of the Zn-MP is due to an ambiguous targeting peptide. Furthermore, we show that the recombinant AtZn-MP degrades mitochondrial and chloroplastic targeting peptides, indicating its function as a signal peptide degrading protease in both mitochondria and chloroplasts.
Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, 10691 Stockholm, Sweden.
Shashi
S
Bhushan
Benoit
B
Lefebvre
Annelie
A
Ståhl
Sarah J
SJ
Wright
Barry D
BD
Bruce
Marc
M
Boutry
Elzbieta
E
Glaser
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology*; D017930:Genes, Reporter; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D011993:Recombinant Fusion Proteins; D008666:Metalloendopeptidases