The bacterial SRP receptor, SecA and the ribosome use overlapping binding sites on the SecY translocon

Patrick Kuhn; Benjamin Weiche; Lukas Sturm; Erik Sommer; Friedel Drepper; Bettina Warscheid; Victor Sourjik; Hans-Georg Koch

doi:10.1111/j.1600-0854.2011.01167.x

The bacterial SRP receptor, SecA and the ribosome use overlapping binding sites on the SecY translocon

Traffic. 2011 May;12(5):563-78. doi: 10.1111/j.1600-0854.2011.01167.x. Epub 2011 Feb 25.

Authors

Patrick Kuhn¹, Benjamin Weiche, Lukas Sturm, Erik Sommer, Friedel Drepper, Bettina Warscheid, Victor Sourjik, Hans-Georg Koch

Affiliation

¹ Institut für Biochemie und Molekularbiologie, ZBMZ, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany.

PMID: 21255212
DOI: 10.1111/j.1600-0854.2011.01167.x

Abstract

Signal recognition particle (SRP)-dependent protein targeting is a universally conserved process that delivers proteins to the bacterial cytoplasmic membrane or to the endoplasmic reticulum membrane in eukaryotes. Crucial during targeting is the transfer of the ribosome-nascent chain complex (RNC) from SRP to the Sec translocon. In eukaryotes, this step is co-ordinated by the SRβ subunit of the SRP receptor (SR), which probably senses a vacant translocon by direct interaction with the translocon. Bacteria lack the SRβ subunit and how they co-ordinate RNC transfer is unknown. By site-directed cross-linking and fluorescence resonance energy transfer (FRET) analyses, we show that FtsY, the bacterial SRα homologue, binds to the exposed C4/C5 loops of SecY, the central component of the bacterial Sec translocon. The same loops serve also as binding sites for SecA and the ribosome. The FtsY-SecY interaction involves at least the A domain of FtsY, which attributes an important function to this so far ill-defined domain. Binding of FtsY to SecY residues, which are also used by SecA and the ribosome, probably allows FtsY to sense an available translocon and to align the incoming SRP-RNC with the protein conducting channel. Thus, the Escherichia coli FtsY encompasses the functions of both the eukaryotic SRα and SRβ subunits in one single protein.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adenosine Triphosphatases / chemistry*
Adenosine Triphosphatases / metabolism
Bacterial Proteins / chemistry*
Bacterial Proteins / genetics
Bacterial Proteins / metabolism
Binding Sites
Escherichia coli / cytology
Escherichia coli / metabolism
Escherichia coli Proteins / chemistry*
Escherichia coli Proteins / genetics
Escherichia coli Proteins / metabolism
Fluorescence Resonance Energy Transfer
Humans
Mass Spectrometry
Membrane Transport Proteins / chemistry*
Membrane Transport Proteins / metabolism
Models, Molecular
Protein Binding
Protein Structure, Tertiary
Protein Subunits / chemistry
Protein Subunits / genetics
Protein Subunits / metabolism
Receptors, Cytoplasmic and Nuclear / chemistry*
Receptors, Cytoplasmic and Nuclear / genetics
Receptors, Cytoplasmic and Nuclear / metabolism
Receptors, Peptide / chemistry*
Receptors, Peptide / genetics
Receptors, Peptide / metabolism
Ribosomes / chemistry*
Ribosomes / metabolism
SEC Translocation Channels
SecA Proteins
Signal Recognition Particle / chemistry*
Signal Recognition Particle / metabolism

Substances

Bacterial Proteins
Escherichia coli Proteins
FtsY protein, Bacteria
Membrane Transport Proteins
Protein Subunits
Receptors, Cytoplasmic and Nuclear
Receptors, Peptide
SEC Translocation Channels
SecY protein, E coli
Signal Recognition Particle
signal peptide receptor
Adenosine Triphosphatases
SecA Proteins