Substrate twinning activates the signal recognition particle and its receptor

Egea, Pascal F.; Shan, Shu‐ou; Napetschnig, Johanna; Savage, David F.; Walter, Peter; Stroud, Rhonda M.

doi:10.1038/nature02250

Cited by 275 publications

(418 citation statements)

References 36 publications

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“…The flexibility of the A domain allows the NG domain to scan a large area for binding to the NG domain of RNC‐bound Ffh/SRP, such that it can recruit an RNC to the translocon by forming the heterodimeric complex of the homologous NG domains17, 18 of translocon‐bound FtsY and RNC‐bound SRP. Thus the A domain of FtsY provides an example for an intrinsically disordered protein region that has a tethering function in a multicomponent protein assembly and illustrates how simple physical principles, such as electrostatic interactions, can drive complex cellular processes, such as the assembly of the quaternary transfer complex at the membrane.…”

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confidence: 99%

“…Electrostatic attraction between the negatively charged central A domain (red) and the positively charged and exposed C4/C5 loop region (blue) of the translocon SecYEG directs FtsY to the translocon. The NG domain of translocon‐bound FtsY searches for the NG domain of RNC‐bound SRP/Ffh (green) to initiate quaternary transfer complex formation by establishing interactions between the NG domains of FtsY and Ffh 17, 18…”

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Electrostatics and Intrinsic Disorder Drive Translocon Binding of the SRP Receptor FtsY

et al. 2016

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Integral membrane proteins in bacteria are co‐translationally targeted to the SecYEG translocon for membrane insertion via the signal recognition particle (SRP) pathway. The SRP receptor FtsY and its N‐terminal A domain, which is lacking in any structural model of FtsY, were studied using NMR and fluorescence spectroscopy. The A domain is mainly disordered and highly flexible; it binds to lipids via its N terminus and the C‐terminal membrane targeting sequence. The central A domain binds to the translocon non‐specifically and maintains disorder. Translocon targeting and binding of the A domain is driven by electrostatic interactions. The intrinsically disordered A domain tethers FtsY to the translocon, and because of its flexibility, allows the FtsY NG domain to scan a large area for binding to the NG domain of ribosome‐bound SRP, thereby promoting the formation of the quaternary transfer complex at the membrane.

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Electrostatics and Intrinsic Disorder Drive Translocon Binding of the SRP Receptor FtsY

et al. 2016

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“…In addition, an inhibitory element from the first helix of the N-domain is removed (Neher et al, 2008). These structural rearrangements bring the two N-domains into proximity with one another, allowing them to make additional interface contacts that stabilize the complex (Egea et al, 2004;Focia et al, 2004). After a stable SRP • SR complex is formed, additional conformational rearrangements occur in both GTPase active sites to activate GTP hydrolysis within the complex .…”

Section: Introductionmentioning

confidence: 99%

“…Both structural and biochemical analyses suggested that these GTPases undergo major structural rearrangements during complex formation (Shan and Walter, 2003;Focia et al, 2004). One of the important conformational changes involves the intramolecular rearrangement at the interface between the N-and the G-domains (Shan and Walter, 2003;Egea et al, 2004;Focia et al, 2004). Two conserved motifs at the N-G-domain interface, ALLEADV on the N-domain and DARGG on the G-domain, act as a fulcrum that mediates the repositioning of the N-domain relaThis article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E08 -10 -0989) on July 8, 2009. tive to the G-domain in both SRP and SR (Focia et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

A Distinct Mechanism to Achieve Efficient Signal Recognition Particle (SRP)–SRP Receptor Interaction by the Chloroplast SRP Pathway

Jaru-Ampornpan

Nguyen

Shan

2009

MBoC

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Cotranslational protein targeting by the signal recognition particle (SRP) requires the SRP RNA, which accelerates the interaction between the SRP and SRP receptor 200-fold. This otherwise universally conserved SRP RNA is missing in the chloroplast SRP (cpSRP) pathway. Instead, the cpSRP and cpSRP receptor (cpFtsY) by themselves can interact 200-fold faster than their bacterial homologues. Here, cross-complementation analyses revealed the molecular origin underlying their efficient interaction. We found that cpFtsY is 5-to 10-fold more efficient than Escherichia coli FtsY at interacting with the GTPase domain of SRP from both chloroplast and bacteria, suggesting that cpFtsY is preorganized into a conformation more conducive to complex formation. Furthermore, the cargo-binding M-domain of cpSRP provides an additional 100-fold acceleration for the interaction between the chloroplast GTPases, functionally mimicking the effect of the SRP RNA in the cotranslational targeting pathway. The stimulatory effect of the SRP RNA or the M-domain of cpSRP is specific to the homologous SRP receptor in each pathway. These results strongly suggest that the M-domain of SRP actively communicates with the SRP and SR GTPases and that the cytosolic and chloroplast SRP pathways have evolved distinct molecular mechanisms (RNA vs. protein) to mediate this communication. INTRODUCTIONThe signal recognition particle (SRP) and the SRP receptor (SR) comprise the major cellular machineries that cotranslationally deliver newly synthesized proteins from the cytosol to target membranes (Walter and Johnson, 1994;Keenan et al., 2001). Cotranslational protein targeting begins with recognition of the cargo-ribosomes translating nascent polypeptides containing signal sequences-by the SRP (Walter et al., 1981). The cargo is brought to the vicinity of the target membrane via the interaction between the SRP and SRP receptor (FtsY in bacteria) (Gilmore et al., 1982a). On arrival at the membrane, SRP unloads its cargo to the protein-conducting channel, composed of the sec61p complex in eukaryotic cells or secYEG complex in bacteria and archaea (Simon and Blobel, 1991;Gorlich et al., 1992;Halic et al., 2006). The SRP and SRP receptor also reciprocally stimulate each other's GTPase activity (Powers and Walter, 1995). Thus, after cargo unloading, guanosine triphosphate (GTP) hydrolysis drives disassembly of the SRP • SR complex, returning the components into the cytosol for the next round of protein targeting (Connolly et al., 1991).The SRP pathway is conserved throughout all three kingdoms of life. Although the protein components of SRP and SR vary across species, the functional core of SRP is a highly conserved ribonucleoprotein complex, composed of a 54-kDa SRP GTPase (SRP54 in eukaryotes or Ffh in bacteria) and an SRP RNA (Keenan et al., 2001). The SRP receptor also contains a conserved GTPase domain that is highly homologous to the GTPase domain in SRP54, and together the GTPase domains of SRP and SR form a unique subgroup in the GTPase superfamily (Keen...

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“…Unlike classical signaling GTPases that undergo large conformational changes depending on whether GTP or guanosine-5Ј-diphosphate (GDP) is bound, the structures of these GTPases are similar regardless of which nucleotide is bound (Freymann et al, 1999;Montoya et al, 1997;Padmanabhan and Freymann, 2001;Gawronski-Salerno et al, 2006;Reyes and Stroud, unpublished data). Substantial conformational changes occur only when the two GTPases form a complex with one another (Egea et al, 2004;Focia et al, 2004). Most notably, the G and N domains readjust their relative positions such that the N domains of both proteins move closer to the dimer interface and form additional interface contacts to stabilize the complex.…”

Section: Introductionmentioning

confidence: 99%

Efficient Interaction between Two GTPases Allows the Chloroplast SRP Pathway to Bypass the Requirement for an SRP RNA

Jaru-Ampornpan

Chandrasekar

Shan

2007

MBoC

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Cotranslational protein targeting to membranes is regulated by two GTPases in the signal recognition particle (SRP) and the SRP receptor; association between the two GTPases is slow and is accelerated 400-fold by the SRP RNA. Intriguingly, the otherwise universally conserved SRP RNA is missing in a novel chloroplast SRP pathway. We found that even in the absence of an SRP RNA, the chloroplast SRP and receptor GTPases can interact efficiently with one another; the kinetics of interaction between the chloroplast GTPases is 400-fold faster than their bacterial homologues, and matches the rate at which the bacterial SRP and receptor interact with the help of SRP RNA. Biochemical analyses further suggest that the chloroplast SRP receptor is pre-organized in a conformation that allows optimal interaction with its binding partner, so that conformational changes during complex formation are minimized. Our results highlight intriguing differences between the classical and chloroplast SRP and SRP receptor GTPases, and help explain how the chloroplast SRP pathway can mediate efficient targeting of proteins to the thylakoid membrane in the absence of the SRP RNA, which plays an indispensable role in all the other SRP pathways.

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Substrate twinning activates the signal recognition particle and its receptor

Cited by 275 publications

References 36 publications

Electrostatics and Intrinsic Disorder Drive Translocon Binding of the SRP Receptor FtsY

Electrostatics and Intrinsic Disorder Drive Translocon Binding of the SRP Receptor FtsY

A Distinct Mechanism to Achieve Efficient Signal Recognition Particle (SRP)–SRP Receptor Interaction by the Chloroplast SRP Pathway

Efficient Interaction between Two GTPases Allows the Chloroplast SRP Pathway to Bypass the Requirement for an SRP RNA

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