The Periplasmic Molecular Chaperone Protein SurA Binds a Peptide Motif That Is Characteristic of Integral Outer Membrane Proteins

Bitto, E.; McKay, David

doi:10.1074/jbc.m308853200

Cited by 130 publications

(148 citation statements)

References 17 publications

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“…Thus, the chaperoning mechanism described here for Skp may be also be important for SurA. However, whereas SurA binding to small peptides has been described (37)(38)(39)(40), the mechanism for protecting ␤-barrels from aggregation remains unclear.…”

Section: Skp Prevents the Aggregation Of Ompa By Forming A Stable Commentioning

confidence: 86%

The cavity-chaperone Skp protects its substrate from aggregation but allows independent folding of substrate domains

Walton

Sandoval

Fowler

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

114

116

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Outer membrane proteins (OMPs) of Gram-negative bacteria are synthesized in the cytosol and must cross the periplasm before insertion into the outer membrane. The 17-kDa protein (Skp) is a periplasmic chaperone that assists the folding and insertion of many OMPs, including OmpA, a model OMP with a membrane embedded ␤-barrel domain and a periplasmic ␣␤ domain. Structurally, Skp belongs to a family of cavity-containing chaperones that bind their substrates in the cavity, protecting them from aggregation. However, some substrates, such as OmpA, exceed the capacity of the chaperone cavity, posing a mechanistic challenge. Here, we provide direct NMR evidence that, while bound to Skp, the ␤-barrel domain of OmpA is maintained in an unfolded state, whereas the periplasmic domain is folded in its native conformation. Complementary cross-linking and NMR relaxation experiments show that the OmpA ␤-barrel is bound deep within the Skp cavity, whereas the folded periplasmic domain protrudes outside of the cavity where it tumbles independently from the rest of the complex. This domain-based chaperoning mechanism allows the transport of ␤-barrels across the periplasm in an unfolded state, which may be important for efficient insertion into the outer membrane.cavity-based ͉ outer membrane M any molecular chaperones have evolved cavity-like structures to bind their non-native substrates. Classic examples, such as the chaperonins, bind the substrate in the cavity formed by their open rings and protect them from aggregation. Cycles of ATP binding and hydrolysis, coupled with substrate binding and release, then help the substrate achieve its native conformation (1). Because the cavities of these chaperones have limited capacities, binding substrates larger than the cavity requires a portion of the substrate to be bound inside the cavity while the rest of the substrate remains outside. In these cases, however, the entire substrate remains unfolded while bound to the open ring of the chaperone (2-4).The 17-kDa protein (Skp) is a periplasmic chaperone present in many Gram-negative bacteria involved in the folding and insertion of proteins in the outer membrane (5-7). The crystal structure of Skp revealed a trimer with a ''jellyfish'' architecture where a central cavity is formed by long tentacle-like helical protrusions emanating from a body domain (Fig. 1A) (8, 9). The Skp structure was unexpectedly similar to that of prefoldin, a cytosolic molecular chaperone present in archea and eukarya (8-10). Although Skp is a trimer (8, 9, 11) and prefoldin is a hexamer (12, 13), both proteins share jellyfish architectures with a central cavity ( Fig. 1 A and B). In prefoldin, this cavity has been shown to bind substrate proteins (10, 13). Prefoldin thus belongs to a family of chaperones sometimes referred to as ''holdases.'' These chaperones are ATP independent and, in contrast to chaperonins, do not directly facilitate folding of their substrates. Instead they protect the substrates from aggregation by holding them in their cavities, and subs...

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Section: Skp Prevents the Aggregation Of Ompa By Forming A Stable Commentioning

confidence: 86%

The cavity-chaperone Skp protects its substrate from aggregation but allows independent folding of substrate domains

Walton

Sandoval

Fowler

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

114

116

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“…BamB crystals appeared 30 -60 days after setup from 0.4 l of BamB at 5.5 mg/ml (in 15 mM Tris (pH 8)) and 0.4 l of reservoir solutions (3.5 M NH 4 Cl, 0.1 M Na-acetate (pH 4.6) or 2 M LiCl, 0.1 M Na-acetate (pH 4.6)). A crystal of the (WD40) 9 degradation product was observed approximately 110 days after setup from 0.4 l of BamB at 16 mg/ml and 0.4 l of ground solution (0.2 M NaCl, 20% PEG 6000, 0.1 M MES (pH 6)).…”

Section: Methodsmentioning

confidence: 99%

“…Structures were solved by the SAD or MIR methods using SHARP for phasing and DM for solvent flattening (27,28). BamB/(WD40) 9 was determined by molecular replacement using the Balbes program (29). Structures were refined using the Refmac program and rebuilt using the Coot program (30).…”

Section: Methodsmentioning

confidence: 99%

“…Various experimental studies describing OMP folding through SurA show the particular importance of this chaperone. Phage display combined with peptide binding studies indicated SurA interactions with amphipathic OMP peptides (9,10). Furthermore, the importance of SurA in vivo is underlined by the observation that E. coli cells being deleted in surA exhibit reduced levels of folded OmpA, OmpC, OmpF, and LamB porins (11).…”

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confidence: 99%

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Structural Basis of Outer Membrane Protein Biogenesis in Bacteria

Albrecht

Zeth

2011

Journal of Biological Chemistry

104

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In Escherichia coli, a multicomponent BAM (␤-barrel assembly machinery) complex is responsible for recognition and assembly of outer membrane ␤-barrel proteins. The functionality of BAM in protein biogenesis is mainly orchestrated through the presence of two essential components, BamA and BamD. Here, we present crystal structures of four lipoproteins (BamB-E). Monomeric BamB and BamD proteins display scaffold architectures typically implied in transient protein interactions. BamB is a ␤-propeller protein comprising eight WD40 repeats. BamD shows an elongated fold on the basis of five tetratricopeptide repeats, three of which form the scaffold for protein recognition. The rod-shaped BamC protein has evolved through the gene duplication of two conserved domains known to mediate protein interactions in structurally related complexes. By contrast, the dimeric BamE is formed through a domain swap and indicates fold similarity to the ␤-lactamase inhibitor protein family, possibly integrating cell wall stability in BAM function. Structural and biochemical data show evidence for the specific recognition of amphipathic sequences through the tetratricopeptide repeat architecture of BamD. Collectively, our data advance the understanding of the BAM complex and highlight the functional importance of BamD in amphipathic outer membrane ␤-barrel protein motif recognition and protein delivery.Gram-negative bacteria are surrounded by two membranes, an inner membrane and the protective outer membrane (OM) 2 layer. The outer membrane architecture is highly asymmetric and composed by integral outer membrane ␤-barrel proteins, lipoproteins, lipopolysaccharides, and phospholipids (1). These components are entirely synthesized in the cytoplasm, translocated over the inner membrane, and finally delivered through the periplasm to the outer membrane by specific shuttle factors that transport their cargo to membrane receptor complexes (1, 2). In Escherichia coli, lipoproteins are targeted to the OM through the LolABCDE complex system via a series of membrane and periplasmic transfer steps (3, 4). Integral OMPs are translocated by the secretion (Sec) machinery and stabilized against premature precipitation or mislocalization in the periplasm by the three major chaperones PpiD, Skp, and SurA (4 -7). These chaperones presumably act sequentially with PpiD at an early stage, early after the OMP release into the periplasm (5). This initial rescue event is followed by Skp and SurA chaperoning at a later stage (8). Various experimental studies describing OMP folding through SurA show the particular importance of this chaperone. Phage display combined with peptide binding studies indicated SurA interactions with amphipathic OMP peptides (9, 10). Furthermore, the importance of SurA in vivo is underlined by the observation that E. coli cells being deleted in surA exhibit reduced levels of folded OmpA, OmpC, OmpF, and LamB porins (11).After the unfolded outer membrane protein is delivered through the periplasmic space, the final steps are the tetherin...

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“…20) and discrete motifs 21 in the sequences of autotransporters that have been conserved through evolution. One conserved motif referred to as 'the b-motif' 21 , appears to act as targeting sequence recognized by the BAM complex [22][23][24][25][26] . A second conserved 'a-linker motif' was found to be situated within the lumen of several autotransporter barrel domains for which crystal structures are available 21 .…”

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confidence: 99%

A mortise–tenon joint in the transmembrane domain modulates autotransporter assembly into bacterial outer membranes

et al. 2014

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Bacterial autotransporters comprise a 12-stranded membrane-embedded b-barrel domain, which must be folded in a process that entraps segments of an N-terminal passenger domain. This first stage of autotransporter folding determines whether subsequent translocation can deliver the N-terminal domain to its functional form on the bacterial cell surface. Here, paired glycine-aromatic 'mortise and tenon' motifs are shown to join neighbouring b-strands in the C-terminal barrel domain, and mutations within these motifs slow the rate and extent of passenger domain translocation to the surface of bacterial cells. In line with this, biophysical studies of the autotransporter Pet show that the conserved residues significantly quicken completion of the folding reaction and promote stability of the autotransporter barrel domain. Comparative genomics demonstrate conservation of glycine-aromatic residue pairings through evolution as a previously unrecognized feature of all autotransporter proteins.

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The Periplasmic Molecular Chaperone Protein SurA Binds a Peptide Motif That Is Characteristic of Integral Outer Membrane Proteins

Cited by 130 publications

References 17 publications

The cavity-chaperone Skp protects its substrate from aggregation but allows independent folding of substrate domains

The cavity-chaperone Skp protects its substrate from aggregation but allows independent folding of substrate domains

Structural Basis of Outer Membrane Protein Biogenesis in Bacteria

A mortise–tenon joint in the transmembrane domain modulates autotransporter assembly into bacterial outer membranes

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