Sec-independent insertion of thylakoid membrane proteins - Analysis of insertion forces and identification of a loop intermediate involving the signal peptide
UNSPECIFIED. (1998) Sec-independent insertion of thylakoid membrane proteins - Analysis of insertion forces and identification of a loop intermediate involving the signal peptide. JOURNAL OF BIOLOGICAL CHEMISTRY, 273 (30). pp. 18979-18983. ISSN 0021-9258Full text not available from this repository.
A group of membrane proteins are synthesized with cleavable signal sequences but inserted into the thylakoid membrane by an unusual Sec/SRP-independent mechanism. In this report we describe a key intermediate in the insertion of one such protein, photosystem II subunit W (PSII-W). A single mutation in the terminal cleavage site partially blocks processing mid leads to the formation of an intermediate-size protein in the thylakoid membrane during chloroplast import assays. This protein is in the form of a loop structure: the N and C termini are exposed on the stromal face, whereas the cleavage site has been translocated into the lumen. In this respect the insertion of this protein resembles that of M13 procoat, which also adopts a loop structure during insertion, and we present preliminary evidence that a similar mechanism is used by another thylakoid protein, PSII-X. However, whereas the negative ly charged region of procoat is translocated by an apparently electrophoretic mechanism using the Delta mu H+, the corresponding region of PSII-W is equally acidic but insertion is Delta mu H+ independent, We furthermore show th.at neutralization of this region has no apparent effect on the insertion process. We propose that a central element in this insertion mechanism is a loop structure whose formation is driven by hydrophobic interactions.
|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:||24 July 1998|
|Number of Pages:||5|
|Page Range:||pp. 18979-18983|
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