Dual Targeting to Mitochondria and Chloroplasts : Characterization of Thr–tRNA Synthetase Targeting Peptide

• There is a group of proteins that are encoded by a single gene,   expressed as a single precursor protein and dually targeted to both   mitochondria and chloroplasts using an ambiguous targeting peptide.   Sequence analysis of 43 dual targeted proteins in comparison with 385   mitochondrial proteins and 567 chloroplast proteins of Arabidopsis   thaliana revealed an overall significant increase in phenylalanines,   leucines, and serines and a decrease in acidic amino acids and glycine   in dual targeting peptides (dTPs). The N-terminal portion of dTPs has   significantly more serines than mTPs. The number of arginines is   similar to those in mTPs, but almost twice as high as those in cTPs. We   have investigated targeting determinants of the dual targeting peptide   of Thr-tRNA synthetase (ThrRS-dTP) studying organellar import of N- and   C-terminal deletion constructs of ThrRS-dTP coupled to GFP. These   results show that the 23 amino acid long N-terminal portion of   ThrRS-dTP is crucial but not sufficient for the organellar import. The   C-terminal deletions revealed that the shortest peptide that was   capable of conferring dual targeting was 60 amino acids long. We have   purified the ThrRS-dTP(2-60) to homogeneity after its expression as a   fusion construct with GST followed by CNBr cleavage and ion exchange   chromatography. The purified ThrRS-dTP(2-60) inhibited import of   pF(1)beta into mitochondria and of pSSU into chloroplasts at mu M   concentrations showing that dual and organelle-specific proteins use   the same organellar import pathways. Furthermore, the CD spectra of   ThrRS-dTP(2-60) indicated that the peptide has the propensity for   forming alpha-helical structure in membrane mimetic environments;   however, the membrane charge was not important for the amount of   induced helical structure. This is the first study in which a dual   targeting peptide has been purified and investigated by biochemical and   biophysical means.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

Dual targeting

mitochondria

chloroplast

targeting peptide

aminoacyl–tRNA synthetase

Biology

Biologi

Biology with specialization in Molecular Biology

Biologi med inriktning mot molekylärbiologi

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)