The major pathways of protein translocation across membranes

Ito, Koreaki

doi:10.1046/j.1365-2443.1996.34034.x

Cited by 35 publications

(32 citation statements)

References 69 publications

(91 reference statements)

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“…125 I-Labeled SecA (4 g) and urea-treated IMVs (60 g of protein) from secY ϩ (EM154; upper panel), secY24 (EM153; middle panel), and secY24 -249 (EM167; lower panel) cells were preincubated at 0°C in a total volume of 230 l, and IMV-SecA complex was isolated by centrifugation, resuspended, and divided into six portions, each of which was then subjected to a SecA insertion reaction at 37°C for 15 min in a total volume of 50 l containing the 125 I-SecA-bound IMV (100 g/ml), pro-3His-OmpAЈ (66 g/ml; lanes 1 and 4), either ATP (2 mM; lanes 1, 2, 4, and 5) or AMP-PNP (2 mM; lanes 3 and 6), and Syd (100 g/ml; lanes [1][2][3]. The samples were treated with trypsin (1000 g/ml at 0°C for 15 min), and the 30-kDa fragment was visualized by SDS-PAGE and autoradiography.…”

Section: Fig 4 Effects Of Syd On Seca Insertion Into Imvsmentioning

confidence: 99%

“…The temperature sensitivity of this mutant is partially suppressible by overproduction of SecE, 2 and the mutation can act as an intragenic suppressor against the SecEsequestering effect of the secY Ϫd 1 mutation (16,20). After solubilization of the membrane with a nonionic detergent, a complex between SecY24 and SecE cannot be isolated (9,16).…”

Section: Fig 4 Effects Of Syd On Seca Insertion Into Imvsmentioning

confidence: 99%

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Syd, a SecY-interacting Protein, Excludes SecA from the SecYE Complex with an Altered SecY24 Subunit

Matsuo¹,

Mori²,

Shimoike³

et al. 1998

Journal of Biological Chemistry

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Syd is an Escherichia coli cytosolic protein that interacts with SecY. Overproduction of this protein causes a number of protein translocation-related phenotypes, including the strong toxicity against the secY24 mutant cells. Previously, this mutation was shown to impair the interaction between SecY and SecE, the two fundamental subunits of the membrane-embedded part of protein translocase. We have now studied in vitro the mechanisms of the Syd-directed inhibition of protein translocation. Pro-OmpA translocation into inverted membrane vesicles (IMVs) prepared from the secY24 mutant cells as well as the accompanied translocation ATPase activity of SecA were rapidly inhibited by purified Syd protein. In the course of protein translocation, high affinity binding of preprotein-bearing SecA to the translocase on the IMV is followed by ATP-driven insertion of the 30-kDa SecA segment into the membrane. Our experiments using 125 I-labeled SecA and the secY24 mutant IMV showed that Syd abolished both the high affinity SecA binding and the SecA insertion. Syd was even able to release the inserted form of SecA that had been stabilized by a nonhydrolyzable ATP analog. Syd affected markedly the proteolytic digestion pattern of the IMVintegrated SecY24 protein, suggesting that Syd exerts its inhibitory effect by interacting directly with the SecY24 protein. In accordance with this notion, a SecY24 variant with a second site mutation (secY249) resisted the Syd action both in vivo and in vitro. Thus, Syd acts against the SecY24 form of translocase, in which SecYSecE interaction has been compromised, to exclude the SecA motor protein from the SecYE channel complex.

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Section: Fig 4 Effects Of Syd On Seca Insertion Into Imvsmentioning

confidence: 99%

Section: Fig 4 Effects Of Syd On Seca Insertion Into Imvsmentioning

confidence: 99%

Syd, a SecY-interacting Protein, Excludes SecA from the SecYE Complex with an Altered SecY24 Subunit

Matsuo¹,

Mori²,

Shimoike³

et al. 1998

Journal of Biological Chemistry

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“…Protein translocation across the Escherichia coli cytoplasmic membrane is catalyzed by a machinery comprising six Sec factors (A, D, E, F, G, and Y) with the help of the secretionspecific molecular chaperone SecB (1)(2)(3)(4)(5)(6). Membrane insertion and deinsertion of SecA coupled to ATP binding and hydrolysis, respectively, have been proposed to be the direct driving force for protein translocation (7,8).…”

mentioning

confidence: 99%

Increases in Acidic Phospholipid Contents Specifically Restore Protein Translocation in a Cold-sensitive secA orsecG Null Mutant

Suzuki

Nishiyama

Tokuda

1999

Journal of Biological Chemistry

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Both the secAcsR11 and ⌬secG::kan mutations cause cold-sensitive growth, although the growth defect due to the latter mutation occurs in a strain-specific manner. Overexpression of pgsA encoding phosphatidylglycerophosphate synthase suppresses the growth defects of the two mutants. We investigated the mechanism underlying the pgsA-dependent suppression of the two mutations using purified mutant SecA and inverted membrane vesicles (IMVs) prepared from pgsA-overexpressing cells. The acidic phospholipid content increased by about 10% upon pgsA overexpression. This increase resulted in the stimulation of proOmpA translocation only when mutant SecA or SecG-depleted IMVs were used.

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“…Protein translocation across the cytoplasmic membrane of Escherichia coli is mediated by a machinery comprising six Sec factors (A, D, E, F, G, and Y) with the help of a secretionspecific molecular chaperone, SecB (4,6,14,20,29,38). The SecA cycle of membrane insertion and deinsertion coupled to ATP binding and hydrolysis, respectively, has been thought to drive protein translocation (8,9).…”

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confidence: 99%

Overexpression of yccL ( gnsA ) and ydfY ( gnsB ) Increases Levels of Unsaturated Fatty Acids and Suppresses both the Temperature-Sensitive fabA6 Mutation and Cold-Sensitive secG Null Mutation of Escherichia coli

et al. 2001

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A multicopy suppressor of the cold-sensitive secG null mutation was isolated. The suppressor contained sfa and yccL, the former of which has been reported to be a multicopy suppressor of the fabA6 mutation carried by a temperature-sensitive unsaturated fatty acid auxotroph. Subcloning of the suppressor gene revealed that yccL, renamed gnsA (secG null mutant suppressor), was responsible for the suppression of both the secG null mutation and the fabA6 mutation. In contrast, the sfa gene did not suppress the fabA6 mutation. The ydfY (gnsB) gene, encoding a protein which is highly similar to GnsA, also suppressed both the secG null mutation and the fabA6 mutation. Although both gnsA and gnsB are linked to cold shock genes, the levels of GnsA and GnsB did not exhibit a cold shock response. A gnsA-gnsB double null mutant grew normally under all conditions examined; thus, the in vivo functions of gnsA and gnsB remain unresolved. However, overexpression of gnsA and gnsB stimulated proOmpA translocation of the secG null mutant at low temperature and caused a significant increase in the unsaturated fatty acid content of phospholipids. Taken together, these results suggest that an increase in membrane fluidity due to the increase in unsaturated fatty acids compensates for the absence of the SecG function, especially at low temperature.

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The major pathways of protein translocation across membranes

Cited by 35 publications

References 69 publications

Syd, a SecY-interacting Protein, Excludes SecA from the SecYE Complex with an Altered SecY24 Subunit

Syd, a SecY-interacting Protein, Excludes SecA from the SecYE Complex with an Altered SecY24 Subunit

Increases in Acidic Phospholipid Contents Specifically Restore Protein Translocation in a Cold-sensitive secA orsecG Null Mutant

Overexpression of yccL ( gnsA ) and ydfY ( gnsB ) Increases Levels of Unsaturated Fatty Acids and Suppresses both the Temperature-Sensitive fabA6 Mutation and Cold-Sensitive secG Null Mutation of Escherichia coli

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