Getting greasy: how transmembrane polypeptide segments integrate into the lipid bilayer

Heijne, Gunnar von

doi:10.1046/j.1365-2958.1997.3351702.x

Cited by 34 publications

(21 citation statements)

References 25 publications

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“…The insertion or translocation of proteins across membranes does not normally occur spontaneously but requires accessory proteins to mediate the passage of large hydrophilic protein domains across the impermeant phospholipid barrier. Protein translocation occurs via well-developed complexes including the ER translocon (von Heijne, 1997), via Sec-dependent secretion in bacteria (von Heijne, 1997), and during import into mitochondria (Stuart and Neupert, 1996). There are, however, examples of posttranslational membrane insertion of mature proteins in the absence of the ER translocon type of system.…”

Section: Discussionmentioning

confidence: 99%

Transmembrane Insertion of theToxoplasma gondiiGRA5 Protein Occurs after Soluble Secretion into the Host Cell

Lecordier

Mercier

Sibley

et al. 1999

MBoC

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The intracellular parasite Toxoplasma gondii resides within a specialized compartment, the parasitophorous vacuole (PV), that resists fusion with host cell endocytic and lysosomal compartments. The PV is extensively modified by secretion of parasite proteins, including the dense granule protein GRA5 that is specifically targeted to the delimiting membrane of the PV (PVM). We show here that GRA5 is present both in a soluble form and in hydrophobic aggregates. GRA5 is secreted as a soluble form into the PV after which it becomes stably associated with the PVM. Topological studies demonstrated that GRA5 was inserted into the PVM as a transmembrane protein with its N-terminal domain extending into the cytoplasm and its C terminus in the vacuole lumen. Deletion of 8 of the 18 hydrophobic amino acids of the single predicted transmembrane domain resulted in the failure of GRA5 to associate with the PVM; yet it remained correctly packaged in the dense granules and was secreted as a soluble protein into the PV.Collectively, these studies demonstrate that the secretory pathway in Toxoplasma is unusual in two regards; it allows soluble export of proteins containing typical transmembrane domains and provides a mechanism for their insertion into a host cell membrane after secretion from the parasite. INTRODUCTIONAmong the varied lifestyles adopted by intracellular parasites is the residence in host cell vacuoles that do not fuse with lysosomes, a strategy exhibited by the protozoan parasite Toxoplasma and the bacterial pathogens Legionella, Chlamydia, and Mycobacteria (Garcia delPortillo and Finlay, 1995). The Toxoplasma-containing vacuole, called the parasitophorous vacuole (PV) 1 , forms by active penetration of the parasite causing invagination of the plasma membrane bilayer (Suss-Toby et al., 1996). This compartment subsequently resists fusion with endosomes and lysosomes by a mechanism that is poorly understood; however, it is clear that the fate of the vacuole is determined at the time of formation (Sibley et al., 1985;Joiner, 1991;Mordue and Sibley, 1997). As the parasite grows and replicates within the cell, it forms a network of tubular membranes that are continuous with the delimiting membrane of the vacuole (Nichols et al., 1983;Sibley et al., 1995).Secretion of proteins stored in apical organelles (micronemes, rhoptries, and dense granules) is a prominent feature of Toxoplasma invasion and presumably contributes both to the nonfusigenic status of the PV and subsequent nutrient uptake by the parasite (Carruthers and Sibley, 1997). Segregated from the endocytic system and cut off from the extracellular fluid, § Corresponding author. E-mail address: mcesbron@infobiogen. fr. † Present address: Laboratory of Molecular Parasitology, Université Libre de Bruxelles, Rhode Saint Genese, Belgium. 1 Abbreviations used: EM, electron microscopy; FBS, fetal bovine serum; F/T, freeze/thaw; HFF, human foreskin fibroblasts; HSP, high-speed pellet; HSS, high-speed supernatant; LSP, lowspeed pellet; LSS, low-speed supernatant; NP-40...

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Section: Discussionmentioning

confidence: 99%

Transmembrane Insertion of theToxoplasma gondiiGRA5 Protein Occurs after Soluble Secretion into the Host Cell

Lecordier

Mercier

Sibley

et al. 1999

MBoC

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“…Addition of 1 mM (final concentration) iodoacetamide to the cultures at the end of growth and in the assay buffer did not affect these results, ruling out artificial in vitro activation of alkaline phosphatase activity (3). The low but appreciable level of alkaline phosphatase activity in the membrane anchor mutant may be due to some leakiness in the function of the membrane anchor as a stop transfer sequence, given that it is shorter than many membrane anchors, which often consist of 20 or more hydrophobic amino acid residues (25).…”

Section: Notes J Bacteriolmentioning

confidence: 99%

Translocon “Pulling” of Nascent SecM Controls the Duration of Its Translational Pause and Secretion-Responsive secA Regulation

2003

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SecA is an ATPase and motor protein that drives protein translocation across the bacterial plasma membrane. In Escherichia coli SecA levels are regulated by the secretion needs of the cell utilizing secM, which encodes a secreted protein. Previous studies demonstrated that this regulation requires a translational pause within secM, whose duration regulates the accessibility of the secA Shine-Dalgarno sequence on secM secA mRNA. Here we provide evidence that translocon "pulling" of nascent SecM is what regulates the duration of the secM translational pause, and thus secA expression levels, thereby providing direct support for this model.

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“…1a). The prediction also includes topological information on the orientation of the transmembrane helices, which is based on the fact that the positively charged residues arginine and lysine are mainly found in non-transmembrane parts of the protein on the cytoplasmic side (von Heijne, 1986(von Heijne, , 1997). The predicted model for the topology of WecA was compared with that of the E. coli MraY protein (Fig.…”

Section: A Topological Model For Wecamentioning

confidence: 99%

Conserved amino acid residues found in a predicted cytosolic domain of the lipopolysaccharide biosynthetic protein WecA are implicated in the recognition of UDP-N-acetylglucosamine

Amer¹,

Valvano²

2001

Microbiology

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Getting greasy: how transmembrane polypeptide segments integrate into the lipid bilayer

Cited by 34 publications

References 25 publications

Transmembrane Insertion of theToxoplasma gondiiGRA5 Protein Occurs after Soluble Secretion into the Host Cell

Transmembrane Insertion of theToxoplasma gondiiGRA5 Protein Occurs after Soluble Secretion into the Host Cell

Translocon “Pulling” of Nascent SecM Controls the Duration of Its Translational Pause and Secretion-Responsive secA Regulation

Conserved amino acid residues found in a predicted cytosolic domain of the lipopolysaccharide biosynthetic protein WecA are implicated in the recognition of UDP-N-acetylglucosamine

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