Sequence analysis and protein import studies of an outer chloroplast envelope polypeptide.
A chloroplast outer envelope membrane protein was cloned and sequenced and from the sequence it was possible to deduce a polypeptide of 6.7 kDa. It has only one membrane-spanning region; the C terminus extends into the cytosol, whereas the N terminus is exposed to the space between the two envelope membranes. The protein was synthesized in an in vitro transcription-translation system to study its routing into isolated chloroplasts. The import studies revealed that the 6.7-kDa protein followed a different and heretofore undescribed translocation pathway in the respect that (i) it does not have a cleavable transit sequence, (ii) it does not require ATP hydrolysis for import, and (iii) protease-sensitive components that are responsible for recognition of precursor proteins destined for the inside of the chloroplasts are not involved in routing the 6.7-kDa polypeptide to the outer chloroplast envelope.
Salomon
M
M
Botanisches Institut, Universität Munich, Federal Republic of Germany.
Fischer
K
K
Flügge
U I
UI
Soll
J
J
D000595:Amino Acid Sequence; D001483:Base Sequence; D002736:Chloroplasts / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D013816:Thermodynamics
D008565:Membrane Proteins