Lipid activation of the signal recognition particle receptor provides spatial coordination of protein targeting

Lam, Vinh; Akopian, David; Rome, Michael E.; Henningsen, Doug; Shan, Shu‐ou

doi:10.1083/jcb.201004129

Cited by 46 publications

(95 citation statements)

References 51 publications

(107 reference statements)

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“…The interaction of FtsY with lipids and the lipid-induced conformational change of the MTS are nucleotide-independent, indicating that lipid association of FtsY via its MTS is independent from its GTPase cycle. The recently shown predominant membrane association of FtsY supports this idea (6), while another study suggests that SRP facilitates the lipid association of FtsY (14).…”

Section: Discussionsupporting

confidence: 58%

“…However, the A domain is not essential in Escherichia coli as a truncation variant (termed NGϩ1) is functional in vivo (11). It was shown that the FtsY GTPase is activated by anionic phospholipids (9) and that the membrane interaction of FtsY is crucial for the release of RNCs from the SRP-FtsY complex (12,13), which was confirmed recently (14). Membrane interaction of E. coli FtsY depends on a conserved motif at the N terminus of the N domain, referred to as membrane-targeting sequence (MTS) (15).…”

mentioning

confidence: 62%

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Lipids Trigger a Conformational Switch That Regulates Signal Recognition Particle (SRP)-mediated Protein Targeting

Stjepanović

Kapp

Bange

et al. 2011

Journal of Biological Chemistry

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Co-translational protein targeting to the membrane is mediated by the signal recognition particle and its receptor (FtsY). Their homologous GTPase domains interact at the membrane and form a heterodimer in which both GTPases are activated. The prerequisite for protein targeting is the interaction of FtsY with phospholipids. However, the mechanism of FtsY regulation by phospholipids remained unclear. Here we show that the N terminus of FtsY (A domain) is natively unfolded in solution and define the complete membrane-targeting sequence. We show that the membrane-targeting sequence is highly dynamic in solution, independent of nucleotides and directly responds to the density of anionic phospholipids by a random coil-helix transition. This conformational switch is essential for tethering FtsY to membranes and activates the GTPase for its subsequent interaction with the signal recognition particle. Our results underline the dynamics of lipid-protein interactions and their importance in the regulation of protein targeting and translocation across biological membranes.The biogenesis of most membrane proteins and many secretory proteins depends on the signal recognition particle (SRP) 4 and the SRP receptor (SR). SRP binds to N-terminal signal sequences of nascent polypeptide chains at the ribosome (ribosome-nascent chain complexes (RNCs)) and acts as an adaptor between the ribosome and the membrane-embedded translocation channel (1-3). Interaction of SRP with SR (FtsY in bacteria and archaea and SR␣ in eukarya) specifies the target membrane and allows for the precise coordination of RNC release from SRP and its transfer to the translocation channel. Protein targeting critically depends on the two homologous GTPases present in SRP and SR forming a heterodimer (4). GTP binding to SRP and SR is required for heterodimer formation and GTP hydrolysis triggers the dissociation of the SRP-SR complex which resets the SRP system for a new round of translocation (5). Although FtsY does not contain a hydrophobic, transmembrane sequence, it was shown to be almost exclusively localized at the membrane (6). FtsY contains three domains: an N-terminal negatively charged A domain of unknown structure and function and the highly conserved N and G domains that form a structural and functional unit, the NG domain (7, 8) (see Fig. 1A). The A domain acts as negative regulator of the FtsY GTPase in a lipid-free environment (9) and was suggested to participate in membrane interaction of FtsY by its N-terminal region (10). However, the A domain is not essential in Escherichia coli as a truncation variant (termed NGϩ1) is functional in vivo (11). It was shown that the FtsY GTPase is activated by anionic phospholipids (9) and that the membrane interaction of FtsY is crucial for the release of RNCs from the SRP-FtsY complex (12, 13), which was confirmed recently (14). Membrane interaction of E. coli FtsY depends on a conserved motif at the N terminus of the N domain, referred to as membrane-targeting sequence (MTS) (15). Recently, strong genetic ...

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Section: Discussionsupporting

confidence: 58%

mentioning

confidence: 62%

Lipids Trigger a Conformational Switch That Regulates Signal Recognition Particle (SRP)-mediated Protein Targeting

Stjepanović

Kapp

Bange

et al. 2011

Journal of Biological Chemistry

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“…However, the identified interactions probably do not dictate docking of the receptor (13). In direct support of a functional interaction between FtsY and lipids, our recent studies revealed that the receptor contains a short and conserved lipid-binding amphipathic ␣-helix at the N-terminal edge of the N domain, which affects the enzymatic behavior of FtsY upon interaction with lipids (13,14), and recent studies further confirmed our conclusions (15). Modeling of the lipid-binding helix of FtsY and its similarity to the MinD membrane targeting sequence (14,16) suggest that the short helix interacts with acidic lipids, as proposed previously (11).…”

supporting

confidence: 72%

Genetic Evidence for Functional Interaction of the Escherichia coli Signal Recognition Particle Receptor with Acidic Lipids in Vivo

Erez

Stjepanović

Zelazny

et al. 2010

Journal of Biological Chemistry

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The mechanism underlying the interaction of the Escherichia coli signal recognition particle receptor FtsY with the cytoplasmic membrane has been studied in detail. Recently, we proposed that FtsY requires functional interaction with inner membrane lipids at a late stage of the signal recognition particle pathway. In addition, an essential lipid-binding ␣-helix was identified in FtsY of various origins. Theoretical considerations and in vitro studies have suggested that it interacts with acidic lipids, but this notion is not yet fully supported by in vivo experimental evidence. Here, we present an unbiased genetic clue, obtained by serendipity, supporting the involvement of acidic lipids. Utilizing a dominant negative mutant of FtsY (termed NG), which is defective in its functional interaction with lipids, we screened for E. coli genes that suppress the negative dominant phenotype. In addition to several unrelated phenotype-suppressor genes, we identified pgsA, which encodes the enzyme phosphatidylglycerophosphate synthase (PgsA). PgsA is an integral membrane protein that catalyzes the committed step to acidic phospholipid synthesis, and we show that its overexpression increases the contents of cardiolipin and phosphatidylglycerol. Remarkably, expression of PgsA also stabilizes NG and restores its biological function. Collectively, our results strongly support the notion that FtsY functionally interacts with acidic lipids.

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“…GTP (guanosine 5′-triphosphate)-driven rearrangements then bring the G domains of both proteins into close contact, giving a stable closed complex (36,37). This rearrangement also exposes a membrane-binding helix of FtsY and thus is coupled to the membrane targeting of cargo (38). Importantly, SRP•FtsY assembly contributes extensively to the fidelity of SRP (39).…”

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confidence: 99%

Regulation by a chaperone improves substrate selectivity during cotranslational protein targeting

Ariosa

Lee

Wang

et al. 2015

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

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The ribosome exit site is a crowded environment where numerous factors contact nascent polypeptides to influence their folding, localization, and quality control. Timely and accurate selection of nascent polypeptides into the correct pathway is essential for proper protein biogenesis. To understand how this is accomplished, we probe the mechanism by which nascent polypeptides are accurately sorted between the major cotranslational chaperone trigger factor (TF) and the essential cotranslational targeting machinery, signal recognition particle (SRP). We show that TF regulates SRP function at three distinct stages, including binding of the translating ribosome, membrane targeting via recruitment of the SRP receptor, and rejection of ribosome-bound nascent polypeptides beyond a critical length. Together, these mechanisms enhance the specificity of substrate selection into both pathways. Our results reveal a multilayered mechanism of molecular interplay at the ribosome exit site, and provide a conceptual framework to understand how proteins are selected among distinct biogenesis machineries in this crowded environment.signal recognition particle | trigger factor | ribosome | protein biogenesis | GTPases P roper protein biogenesis is a prerequisite for the maintenance of a functional proteome. Accumulating data indicate that this process begins at the ribosome exit site, where many protein biogenesis machineries can interact and gain access to the nascent polypeptide. This includes chaperones (1-5) such as trigger factor (TF) (1, 4, 6, 7), Hsp70, and the nascent polypeptide-associated complex (8-13); modification enzymes (10, 14-16) such as N-acetyl transferase, methionine aminopeptidase, and arginyl transferase; protein-targeting and translocation machineries such as signal recognition particle (SRP) (17-20), SecA (21), the SecYEG (or Sec61p) (22, 23) and YidC translocases (24,25), and the ribosome-bound quality control complex (26)(27)(28)(29)(30). Engagement of these factors with nascent polypeptides influences their folding, assembly, localization, processing, and quality control. Within seconds after the nascent polypeptide emerges from the ribosomal exit tunnel, it must engage the correct set of factors and thus commit to the proper biogenesis pathway. How this is accomplished in the crowded environment at the ribosome exit site is an emerging question. In this work, we address this question by deciphering how nascent proteins are selected between two major protein biogenesis machineries in bacteria, SRP and TF.SRP is a universally conserved ribonucleoprotein complex responsible for the cotranslational targeting of proteins to the eukaryotic endoplasmic reticulum (ER), or the bacterial plasma membrane (31). SRP recognizes ribosome-nascent chain complexes (termed RNC or cargo) carrying strong signal sequences and delivers them to the SecYEG or YidC translocation machinery on the target membrane. SRP binds RNC via two interactions: a helical N domain in the SRP54 protein (called Ffh in bacteria) binds the ribosoma...

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Lipid activation of the signal recognition particle receptor provides spatial coordination of protein targeting

Abstract: Phospholipid binding leads to accelerated assembly of the bacterial SRP receptor FtsY and SRP, allowing cargo proteins to be delivered to target membranes more efficiently.

Cited by 46 publications

References 51 publications

Lipids Trigger a Conformational Switch That Regulates Signal Recognition Particle (SRP)-mediated Protein Targeting

Lipids Trigger a Conformational Switch That Regulates Signal Recognition Particle (SRP)-mediated Protein Targeting

Genetic Evidence for Functional Interaction of the Escherichia coli Signal Recognition Particle Receptor with Acidic Lipids in Vivo

Regulation by a chaperone improves substrate selectivity during cotranslational protein targeting

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