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Structures of the signal recognition particle receptor from the archaeon Pyrococcus furiosus: implications for the targeting step at the membrane.

Egea PF, Tsuruta H, de Leon GP, Napetschnig J, Walter P, Stroud RM - PLoS ONE (2008)

Bottom Line: The basic charges on the surface of this helix are likely to regulate interactions at the membrane.Small angle X-ray scattering and analytical ultracentrifugation indicate that the crystal structure of Pfu-FtsY correlates well with the average conformation in solution.Based on previous structures of two sub-complexes, we propose a model of the core of archeal and eukaryotic SRP*SR targeting complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA. pascal@msg.ucsf.edu

ABSTRACT
In all organisms, a ribonucleoprotein called the signal recognition particle (SRP) and its receptor (SR) target nascent proteins from the ribosome to the translocon for secretion or membrane insertion. We present the first X-ray structures of an archeal FtsY, the receptor from the hyper-thermophile Pyrococcus furiosus (Pfu), in its free and GDP*magnesium-bound forms. The highly charged N-terminal domain of Pfu-FtsY is distinguished by a long N-terminal helix. The basic charges on the surface of this helix are likely to regulate interactions at the membrane. A peripheral GDP bound near a regulatory motif could indicate a site of interaction between the receptor and ribosomal or SRP RNAs. Small angle X-ray scattering and analytical ultracentrifugation indicate that the crystal structure of Pfu-FtsY correlates well with the average conformation in solution. Based on previous structures of two sub-complexes, we propose a model of the core of archeal and eukaryotic SRP*SR targeting complexes.

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Comparison of the different SRP receptors.(A) The six available FtsY structures shown in the same relative orientation. In each case the helix αN1 in the N domain and the α7 C-terminal helix in the G domain are colored in yellow and red, respectively. An asterisk indicates the N-terminal extension observed in all FtsYs except Pfu. The sites of proteolysis observed in E.coli and Taq FtsYs upon Ffh•FtsY complex formation are also indicated (x). (B) Close-up view of the overlaid six FtsY structures showing the αN1 and α7 terminal helices. (C) Superposition of the Pfu and Taq FtsYs emphasizing the shape anisotropy of Pfu-FtsY due to the long αN1 terminal helix in its N domain. Distances along the longest axis of inertia are indicated.
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pone-0003619-g004: Comparison of the different SRP receptors.(A) The six available FtsY structures shown in the same relative orientation. In each case the helix αN1 in the N domain and the α7 C-terminal helix in the G domain are colored in yellow and red, respectively. An asterisk indicates the N-terminal extension observed in all FtsYs except Pfu. The sites of proteolysis observed in E.coli and Taq FtsYs upon Ffh•FtsY complex formation are also indicated (x). (B) Close-up view of the overlaid six FtsY structures showing the αN1 and α7 terminal helices. (C) Superposition of the Pfu and Taq FtsYs emphasizing the shape anisotropy of Pfu-FtsY due to the long αN1 terminal helix in its N domain. Distances along the longest axis of inertia are indicated.

Mentions: To date structures of six SRs have been reported; these include the bacterial receptors, [18], [19], Taq [20], Tma [21], Mmyc [14], and the eukaryotic organelle-specific chloroplastic SR from Atha [22], [23]. Our Pfu-FtsY structure is the first representative from the Archaea kingdom. The Pfu-FtsY N domain is unusual in several aspects. While it retains the canonical four α-helical bundle fold observed in all SRP GTPases, it has an additional two-stranded anti-parallel β-sheet not seen in the other FtsY structures; βN1 is inserted between helices αN1-αN2, and βN2 is inserted between αN3-αN4 (Figures 1A). βN1 and βN2 assemble together to form a flat surface exposed at the tip of the N domain (Figure 1B). The αN1 helix of Pfu-FtsY, whose N terminus is perfectly defined, is 44Å-long and is a single secondary structure element with no bending or disorder. This helix protrudes out of the N domain (Figure 1B and 4A). While the position of the C-terminal helix α7 is conserved in all SRs (Figure 4B), helix αN1 of the non-archeal homologues is bent, resulting in an N terminal extension that packs against the surface of the N/G domain including C terminal helix α7 (Figures 4A and 4B). The αN1 helix of Pfu-FtsY is not bent and its axis is shifted towards the core of the four α-helix bundle resulting in an overall more compact, albeit extended, N domain.


Structures of the signal recognition particle receptor from the archaeon Pyrococcus furiosus: implications for the targeting step at the membrane.

Egea PF, Tsuruta H, de Leon GP, Napetschnig J, Walter P, Stroud RM - PLoS ONE (2008)

Comparison of the different SRP receptors.(A) The six available FtsY structures shown in the same relative orientation. In each case the helix αN1 in the N domain and the α7 C-terminal helix in the G domain are colored in yellow and red, respectively. An asterisk indicates the N-terminal extension observed in all FtsYs except Pfu. The sites of proteolysis observed in E.coli and Taq FtsYs upon Ffh•FtsY complex formation are also indicated (x). (B) Close-up view of the overlaid six FtsY structures showing the αN1 and α7 terminal helices. (C) Superposition of the Pfu and Taq FtsYs emphasizing the shape anisotropy of Pfu-FtsY due to the long αN1 terminal helix in its N domain. Distances along the longest axis of inertia are indicated.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2572998&req=5

pone-0003619-g004: Comparison of the different SRP receptors.(A) The six available FtsY structures shown in the same relative orientation. In each case the helix αN1 in the N domain and the α7 C-terminal helix in the G domain are colored in yellow and red, respectively. An asterisk indicates the N-terminal extension observed in all FtsYs except Pfu. The sites of proteolysis observed in E.coli and Taq FtsYs upon Ffh•FtsY complex formation are also indicated (x). (B) Close-up view of the overlaid six FtsY structures showing the αN1 and α7 terminal helices. (C) Superposition of the Pfu and Taq FtsYs emphasizing the shape anisotropy of Pfu-FtsY due to the long αN1 terminal helix in its N domain. Distances along the longest axis of inertia are indicated.
Mentions: To date structures of six SRs have been reported; these include the bacterial receptors, [18], [19], Taq [20], Tma [21], Mmyc [14], and the eukaryotic organelle-specific chloroplastic SR from Atha [22], [23]. Our Pfu-FtsY structure is the first representative from the Archaea kingdom. The Pfu-FtsY N domain is unusual in several aspects. While it retains the canonical four α-helical bundle fold observed in all SRP GTPases, it has an additional two-stranded anti-parallel β-sheet not seen in the other FtsY structures; βN1 is inserted between helices αN1-αN2, and βN2 is inserted between αN3-αN4 (Figures 1A). βN1 and βN2 assemble together to form a flat surface exposed at the tip of the N domain (Figure 1B). The αN1 helix of Pfu-FtsY, whose N terminus is perfectly defined, is 44Å-long and is a single secondary structure element with no bending or disorder. This helix protrudes out of the N domain (Figure 1B and 4A). While the position of the C-terminal helix α7 is conserved in all SRs (Figure 4B), helix αN1 of the non-archeal homologues is bent, resulting in an N terminal extension that packs against the surface of the N/G domain including C terminal helix α7 (Figures 4A and 4B). The αN1 helix of Pfu-FtsY is not bent and its axis is shifted towards the core of the four α-helix bundle resulting in an overall more compact, albeit extended, N domain.

Bottom Line: The basic charges on the surface of this helix are likely to regulate interactions at the membrane.Small angle X-ray scattering and analytical ultracentrifugation indicate that the crystal structure of Pfu-FtsY correlates well with the average conformation in solution.Based on previous structures of two sub-complexes, we propose a model of the core of archeal and eukaryotic SRP*SR targeting complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA. pascal@msg.ucsf.edu

ABSTRACT
In all organisms, a ribonucleoprotein called the signal recognition particle (SRP) and its receptor (SR) target nascent proteins from the ribosome to the translocon for secretion or membrane insertion. We present the first X-ray structures of an archeal FtsY, the receptor from the hyper-thermophile Pyrococcus furiosus (Pfu), in its free and GDP*magnesium-bound forms. The highly charged N-terminal domain of Pfu-FtsY is distinguished by a long N-terminal helix. The basic charges on the surface of this helix are likely to regulate interactions at the membrane. A peripheral GDP bound near a regulatory motif could indicate a site of interaction between the receptor and ribosomal or SRP RNAs. Small angle X-ray scattering and analytical ultracentrifugation indicate that the crystal structure of Pfu-FtsY correlates well with the average conformation in solution. Based on previous structures of two sub-complexes, we propose a model of the core of archeal and eukaryotic SRP*SR targeting complexes.

Show MeSH