FtsY Binds to the Escherichia coli Inner Membrane via Interactions with Phosphatidylethanolamine and Membrane Proteins

Millman, Jonathan; Qi, Haiyan; Vulcu, Felicia; Bernstein, Harris; Andrews, David W.

doi:10.1074/jbc.m011331200

Cited by 53 publications

(62 citation statements)

References 41 publications

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“…15 and this study), we show that the MTS is highly dynamic in solution. Previous studies showed that FtsY has a preference for anionic phospholipids (9), whereas other studies also suggested a role of zwitterionic lipids (36). The current study clarifies that only the interaction with anionic phospholipids triggers a random-coil helix transition of the MTS.…”

Section: Discussionsupporting

confidence: 61%

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: 61%

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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“…20). This proposal has been confirmed several times by demonstrating that FtsY assembles on membranes via interactions with a trypsin-sensitive component (22,37). Finally, the most compelling evidence for FtsYmembrane protein association has recently been offered by studies of the interaction between FtsY and the SecYEG complex in E. coli (11,12).…”

Section: Discussionmentioning

confidence: 54%

“…Moreover, at least one determinant of lipid interaction was identified as the NG domain. In contrast to acidic lipids, other studies proposed that FtsY assembles on membranes via interactions with phosphatidylethanolamine, through the AN domain (37). Regardless of the crucial differences in identifying the specific lipids (see later), the combined studies implied a role for the N-domain in lipid binding.…”

Section: Discussionmentioning

confidence: 94%

Escherichia coli Signal Recognition Particle Receptor FtsY Contains an Essential and Autonomous Membrane-binding Amphipathic Helix

Parlitz

Eitan

Stjepanović

et al. 2007

Journal of Biological Chemistry

119

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“…Strong support for functional interaction of FtsY with lipids, preferentially acidic ones, was obtained by in vitro studies, which demonstrated marked stimulation of the FtsY GTPase activity by lipids (15). On the other hand, it has been shown that a postulated FtsY membrane assembly domain binds to E. coli inner membrane inverted vesicles via an interaction with a trypsin-sensitive component (28) and that FtsY is associated with the translocon (7,8). Based on these and additional data, a model was proposed that FtsY binding to the membrane occurs initially through phospholipid binding, followed by targeting to translocation sites via an interaction with an unknown membrane protein.…”

Section: Discussionmentioning

confidence: 97%

Membrane Targeting of Ribosomes and Their Release Require Distinct and Separable Functions of FtsY

Bahari

Parlitz

Eitan

et al. 2007

Journal of Biological Chemistry

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The mechanism underlying the interaction of the Escherichia coli signal recognition particle (SRP) receptor FtsY with the cytoplasmic membrane is not fully understood. We investigated this issue by utilizing active (NG؉1) and inactive (NG) mutants of FtsY. In solution, the mutants comparably bind and hydrolyze nucleotides and associate with SRP. In contrast, a major difference was observed in the cellular distribution of NG and NG؉1. Unlike NG؉1, which distributes almost as the wild-type receptor, the inactive NG mutant accumulates on the membrane, together with ribosomes and SRP. The results suggest that NG function is compromised only at a later stage of the targeting pathway and that despite their identical behavior in solution, the membrane-bound NG-SRP complex is less active than NG؉1-SRP. This notion is strongly supported by the observation that lipids stimulate the GTPase activity of NG؉1-SRP, whereas no stimulation is observed with NG-SRP. In conclusion, we propose that the SRP receptor has two distinct and separable roles in (i) mediating membrane targeting and docking of ribosomes and (ii) promoting their productive release from the docking site.Membrane-bound ribosomes are responsible for the biosynthesis of many integral membrane proteins that insert into the membrane in a co-translational manner (1, 2). Targeting of these ribosomes to the cytoplasmic membrane in Escherichia coli requires the signal recognition particle (SRP) 2 receptor, FtsY (3). In addition, under FtsY depletion conditions, the expression of polytopic membrane proteins such as LacY (4), SecY (3), and MdfA 3 is repressed. Besides its interaction with the inner membrane, FtsY functionally interacts with the SRP and the SRP protein Ffh in a nucleotide-dependent manner (reviewed in Ref. 5). Moreover, additional studies demonstrated that FtsY forms a complex with membrane-bound ribosomes (6) and the SecYEG translocon (7, 8). These observations thus underscore the central role of the SRP receptor in ribosome targeting and biogenesis of membrane proteins (1, 9). However, despite extensive genetic, biochemical, and structural studies, important aspects of the function of FtsY are not yet fully understood.At steady state, FtsY is distributed between the cytoplasm and the membrane (10), but the cytosolic form does not seem to be essential for membrane protein biogenesis or cell survival (11). In contrast, various studies suggest that FtsY functions as a membrane-bound receptor (11, 12), in agreement with observations that it interacts with membrane-bound ribosomes (6) and the translocon (7,8). Interestingly, however, FtsY has no known membrane anchor partner homologous to the mammalian ␤-subunit of the SRP receptor.FtsY contains three domains. The C-terminal N-and G-domains (together 302 residues long) constitute a universally conserved SRP-GTPase (13) that interacts with the homologous NG domain of the SRP protein Ffh. In its N terminus, FtsY contains an acidic A-domain (195 residues long) that was proposed to mediate membrane targeting and...

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FtsY Binds to the Escherichia coli Inner Membrane via Interactions with Phosphatidylethanolamine and Membrane Proteins

Cited by 53 publications

References 41 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

Escherichia coli Signal Recognition Particle Receptor FtsY Contains an Essential and Autonomous Membrane-binding Amphipathic Helix

Membrane Targeting of Ribosomes and Their Release Require Distinct and Separable Functions of FtsY

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