Functional domains of the ferredoxin transit sequence involved in chloroplast import.
In order to analyze the information content of a chloroplast transit sequence, we have constructed and analyzed by in vitro assays seven substitution and 20 deletion mutants of the ferredoxin transit sequence. The N-terminal part and the C-terminal part are important for targeting, and in addition the C-terminal region is required for processing. A third region is important for translocation but not for the initial interaction with the envelope. A fourth region is less essential for in vitro import. Purified precursors were tested for their ability to compete for the in vitro import of radiolabeled wild-type precursor, which confirmed the important role in chloroplast recognition of both the N- and the C-terminal domain of the transit sequence. Monolayer experiments showed that the N terminus was mainly involved in the insertion into mono-galactolipid-containing lipid surfaces whereas the C terminus mediates the recognition of negatively charged lipids. A sequence comparison to other transit sequences suggests that the domain structure of the ferredoxin transit sequence can be extended to these sequences and thus reveals a general structural design of transit sequences.
Pilon
M
M
Institute of Biomembranes, Utrecht University, The Netherlands.
Wienk
H
H
Sips
W
W
de Swaaf
M
M
Talboom
I
I
van 't Hof
R
R
de Korte-Kool
G
G
Demel
R
R
Weisbeek
P
P
de Kruijff
B
B
D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002736:Chloroplasts / Q000378:metabolism*; D005288:Ferredoxins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009838:Oligodeoxyribonucleotides; D011499:Protein Processing, Post-Translational; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
D005288:Ferredoxins; D009838:Oligodeoxyribonucleotides