Dual signal peptides mediate the signal recognition particle Sec-independent insertion of a thylakoid membrane polyprotein, psbY
UNSPECIFIED (1999) Dual signal peptides mediate the signal recognition particle Sec-independent insertion of a thylakoid membrane polyprotein, psbY. JOURNAL OF BIOLOGICAL CHEMISTRY, 274 (7). pp. 4059-4066. ISSN 0021-9258Full text not available from this repository.
The nuclear psbY gene (formerly ycf32) encodes two distinct single-spanning chloroplast thylakoid membrane proteins in Arabidopsis thaliana, After import into the chloroplast, the precursor protein is processed to a polyprotein in which each "mature" protein is preceded by an additional hydrophobic region; we show that these regions function as signal peptides that are cleaved after insertion into the thylakoid membrane. Inhibition of the first or second signal cleavage reaction by enlargement of the -1 residues leads in each case to the accumulation of a thylakoid-integrated intermediate containing three hydrophobic regions after import into chloroplasts; a double mutant is converted to a protein containing all four hydrophobic regions. We propose that the overall insertion process involves (i) insertion as a double-loop structure, (ii) two cleavages by the thylakoidal processing peptidase on the lumenal face of the membrane, and (iii) cleavage by an unknown peptidase on the stromal face on the membrane between the first mature protein and the second signal peptide. We also show that this polyprotein can insert into the thylakoid membrane in the absence of stromal factors, nucleoside triphosphates, or a functional Sec apparatus; this effectively shows for the first time that a multispanning protein can insert posttranslationally without the aid of signal recognition particle, SecA, or the membrane-bound Sec machinery.
|Item Type:||Journal Article|
|Subjects:||Q Science > QD Chemistry|
|Journal or Publication Title:||JOURNAL OF BIOLOGICAL CHEMISTRY|
|Publisher:||AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC|
|Date:||12 February 1999|
|Number of Pages:||8|
|Page Range:||pp. 4059-4066|
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