scholarly journals Membrane binding of the bacterial signal recognition particle receptor involves two distinct binding sites

2006 ◽  
Vol 174 (5) ◽  
pp. 715-724 ◽  
Author(s):  
Sandra Angelini ◽  
Diana Boy ◽  
Emile Schiltz ◽  
Hans-Georg Koch
Keyword(s):  
Binding Sites ◽  
Protein Targeting ◽  
Cytoplasmic Membrane ◽  
Signal Recognition Particle ◽  
Membrane Association ◽  
Signal Recognition ◽  
Gtpase Activity ◽  
Signal Recognition Particle Receptor ◽  
Membrane Anchoring ◽  
Lipid Anchor

Cotranslational protein targeting in bacteria is mediated by the signal recognition particle (SRP) and FtsY, the bacterial SRP receptor (SR). FtsY is homologous to the SRα subunit of eukaryotes, which is tethered to the membrane via its interaction with the membrane-integral SRβ subunit. Despite the lack of a membrane-anchoring subunit, 30% of FtsY in Escherichia coli are found stably associated with the cytoplasmic membrane. However, the mechanisms that are involved in this membrane association are only poorly understood. Our data indicate that membrane association of FtsY involves two distinct binding sites and that binding to both sites is stabilized by blocking its GTPase activity. Binding to the first site requires only the NG-domain of FtsY and confers protease protection to FtsY. Importantly, the SecY translocon provides the second binding site, to which FtsY binds to form a carbonate-resistant 400-kD FtsY–SecY translocon complex. This interaction is stabilized by the N-terminal A-domain of FtsY, which probably serves as a transient lipid anchor.

scholarly journals The Membrane-binding Motif of the Chloroplast Signal Recognition Particle Receptor (cpFtsY) Regulates GTPase Activity

2009 ◽  
Vol 284 (22) ◽  
pp. 14891-14903 ◽  
Author(s):  
Naomi J. Marty ◽  
Dakshinamurthy Rajalingam ◽  
Alicia D. Kight ◽  
Nathaniel E. Lewis ◽  
Daniel Fologea ◽  
...  
Keyword(s):  
Signal Recognition Particle ◽  
Membrane Binding ◽  
Binding Motif ◽  
Signal Recognition ◽  
Gtpase Activity ◽  
Signal Recognition Particle Receptor

scholarly journals The beta subunit of the signal recognition particle receptor is a transmembrane GTPase that anchors the alpha subunit, a peripheral membrane GTPase, to the endoplasmic reticulum membrane.

1995 ◽  
Vol 128 (3) ◽  
pp. 273-282 ◽  
Author(s):  
J D Miller ◽  
S Tajima ◽  
L Lauffer ◽  
P Walter
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Targeting ◽  
Signal Sequence ◽  
Transmembrane Protein ◽  
Signal Recognition Particle ◽  
Endoplasmic Reticulum Membrane ◽  
Protein Chain ◽  
Signal Recognition ◽  
Signal Recognition Particle Receptor ◽  
Er Membrane

The signal recognition particle receptor (SR) is required for the cotranslational targeting of both secretory and membrane proteins to the endoplasmic reticulum (ER) membrane. During targeting, the SR interacts with the signal recognition particle (SRP) which is bound to the signal sequence of the nascent protein chain. This interaction catalyzes the GTP-dependent transfer of the nascent chain from SRP to the protein translocation apparatus in the ER membrane. The SR is a heterodimeric protein comprised of a 69-kD subunit (SR alpha) and a 30-kD subunit (SR beta) which are associated with the ER membrane in an unknown manner. SR alpha and the 54-kD subunits of SRP (SRP54) each contain related GTPase domains which are required for SR and SRP function. Molecular cloning and sequencing of a cDNA encoding SR beta revealed that SR beta is a transmembrane protein and, like SR alpha and SRP54, is a member of the GTPase superfamily. Although SR beta defines its own GTPase subfamily, it is distantly related to ARF and Sar1. Using UV cross-linking, we confirm that SR beta binds GTP specifically. Proteolytic digestion experiments show that SR alpha is required for the interaction of SRP with SR. SR alpha appears to be peripherally associated with the ER membrane, and we suggest that SR beta, as an integral membrane protein, mediates the membrane association of SR alpha. The discovery of its guanine nucleotide-binding domain, however, makes it likely that its role is more complex than that of a passive anchor for SR alpha. These findings suggest that a cascade of three directly interacting GTPases functions during protein targeting to the ER membrane.

scholarly journals Protein Targeting to the Bacterial Cytoplasmic Membrane

1999 ◽  
Vol 63 (1) ◽  
pp. 161-173 ◽  
Author(s):  
Peter Fekkes ◽  
Arnold J. M. Driessen
Keyword(s):  
Protein Targeting ◽  
Cytoplasmic Membrane ◽  
Signal Sequence ◽  
Specific Interaction ◽  
Signal Recognition Particle ◽  
High Fidelity ◽  
Signal Recognition ◽  
Nascent Chain ◽  
Major Route ◽  
Mature Domain

SUMMARY Proteins that perform their activity within the cytoplasmic membrane or outside this cell boundary must be targeted to the translocation site prior to their insertion and/or translocation. In bacteria, several targeting routes are known; the SecB- and the signal recognition particle-dependent pathways are the best characterized. Recently, evidence for the existence of a third major route, the twin-Arg pathway, was gathered. Proteins that use either one of these three different pathways possess special features that enable their specific interaction with the components of the targeting routes. Such targeting information is often contained in an N-terminal extension, the signal sequence, but can also be found within the mature domain of the targeted protein. Once the nascent chain starts to emerge from the ribosome, competition for the protein between different targeting factors begins. After recognition and binding, the targeting factor delivers the protein to the translocation sites at the cytoplasmic membrane. Only by means of a specific interaction between the targeting component and its receptor is the cargo released for further processing and translocation. This mechanism ensures the high-fidelity targeting of premembrane and membrane proteins to the translocation site.

scholarly journals The Ribosome Regulates the Gtpase of the β-Subunit of the Signal Recognition Particle Receptor

1999 ◽  
Vol 146 (4) ◽  
pp. 723-730 ◽  
Author(s):  
Gerald Bacher ◽  
Martin Pool ◽  
Bernhard Dobberstein
Keyword(s):  
Protein Targeting ◽  
Signal Sequence ◽  
Signal Recognition Particle ◽  
Bound State ◽  
Signal Recognition ◽  
Β Subunit ◽  
Gtp Hydrolysis ◽  
Signal Recognition Particle Receptor ◽  
Membrane Bound ◽  
Gtpase Cycle

Protein targeting to the membrane of the ER is regulated by three GTPases, the 54-kD subunit of the signal recognition particle (SRP) and the α- and β-subunit of the SRP receptor (SR). Here, we report on the GTPase cycle of the β-subunits of the SR (SRβ). We found that SRβ binds GTP with high affinity and interacts with ribosomes in the GTP-bound state. Subsequently, the ribosome increases the GTPase activity of SRβ and thus functions as a GTPase activating protein for SRβ. Furthermore, the interaction between SRβ and the ribosome leads to a reduction in the affinity of SRβ for guanine nucleotides. We propose that SRβ regulates the interaction of SR with the ribosome and thereby allows SRα to scan membrane-bound ribosomes for the presence of SRP. Interaction between SRP and SRα then leads to release of the signal sequence from SRP and insertion into the translocon. GTP hydrolysis then results in dissociation of SR from the ribosome, and SRP from the SR.

scholarly journals Structural analysis of the SRP Alu domain from Plasmodium falciparum reveals a non-canonical open conformation

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Komal Soni ◽  
Georg Kempf ◽  
Karen Manalastas-Cantos ◽  
Astrid Hendricks ◽  
Dirk Flemming ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Binding Sites ◽  
Signal Recognition Particle ◽  
Signal Recognition ◽  
Closed Conformation ◽  
Open Conformation ◽  
Structural Database ◽  
Alu Rna ◽  
Species Specific ◽  
Protozoan Species

AbstractThe eukaryotic signal recognition particle (SRP) contains an Alu domain, which docks into the factor binding site of translating ribosomes and confers translation retardation. The canonical Alu domain consists of the SRP9/14 protein heterodimer and a tRNA-like folded Alu RNA that adopts a strictly ‘closed’ conformation involving a loop-loop pseudoknot. Here, we study the structure of the Alu domain from Plasmodium falciparum (PfAlu), a divergent apicomplexan protozoan that causes human malaria. Using NMR, SAXS and cryo-EM analyses, we show that, in contrast to its prokaryotic and eukaryotic counterparts, the PfAlu domain adopts an ‘open’ Y-shaped conformation. We show that cytoplasmic P. falciparum ribosomes are non-discriminative and recognize both the open PfAlu and closed human Alu domains with nanomolar affinity. In contrast, human ribosomes do not provide high affinity binding sites for either of the Alu domains. Our analyses extend the structural database of Alu domains to the protozoan species and reveal species-specific differences in the recognition of SRP Alu domains by ribosomes.

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