Membrane Insertion of the M13 Minor Coat Protein G3p Is Dependent on YidC and the SecAYEG Translocase.

Farina Kleinbeck,Andreas Kuhn

doi:10.3390/v13071414

Abstract

The minor coat protein G3p of bacteriophage M13 is the key component for the host interaction of this virus and binds to Escherichia coli at the tip of the F pili. As we show here, during the biosynthesis of G3p as a preprotein, the signal sequence interacts primarily with SecY, whereas the hydrophobic anchor sequence at the C-terminus interacts with YidC. Using arrested nascent chains and thiol crosslinking, we show here that the ribosome-exposed signal sequence is first contacted by SecY but not by YidC, suggesting that only SecYEG is involved at this early stage. The protein has a large periplasmic domain, a hydrophobic anchor sequence of 21 residues and a short C-terminal tail that remains in the cytoplasm. During the later synthesis of the entire G3p, the residues 387, 389 and 392 in anchor domain contact YidC in its hydrophobic slide to hold translocation of the C-terminal tail. Finally, the protein is processed by leader peptidase and assembled into new progeny phage particles that are extruded out of the cell.

Highlights

The M13 G3p is synthesised with an 18-amino-acid-residue-long signal sequence, a large periplasmic domain of 379 residues, a 21-residue-long membrane anchor domain and a C-terminal tail of six residues located in the cytoplasm (Figure 1)
Most membrane proteins are targeted by the signal recognition particle SRP, consisting of the Ffh protein and a 4.5S RNA in Escherichia coli
Our results show that the membrane insertion of G3p requires SecA, SecYEG, YidC and the membrane potential across the inner membrane

Summary

Introduction

The M13 G3p is synthesised with an 18-amino-acid-residue-long signal sequence, a large periplasmic domain of 379 residues, a 21-residue-long membrane anchor domain and a C-terminal tail of six residues located in the cytoplasm (Figure 1). This allows the newly synthesised protein to insert into the inner membrane of Escherichia coli before its assembly into the phage progeny particles [1]. The periplasmic part of G3p folds into β-structured N1 and N2 domains that are separated by glycine-rich regions The membrane-spanning protein is assembled onto the proximal end of the phage particles that are extruded from the infected cells.

Methods

Results

Discussion

Conclusion