Signal recognition particle mediated protein targeting in Escherichia coli.

The signal recognition particle (SRP) is a conserved ribonucleoprotein complex that binds to targeting sequences in nascent secretory and membrane proteins. The SRP guides these proteins to the cytoplasmic membrane in prokaryotes and the endoplasmic reticulum membrane in eukaryotes via an interaction with its cognate receptor. The E.

Epitope tagging analysis of the outer membrane folding of the molecular usher FaeD involved in K88 fimbriae biosynthesis in Escherichia coli.

To analyse the outer membrane folding of the molecular usher FaeD, tagged derivatives were prepared and their expression, tag-localisation and functioning in K88 fimbriae biosynthesis was studied. A semi-random insertion mutagenesis approach with factor Xa cleavage sites yielded six tagged FaeD derivatives. A site-directed mutagenesis approach in which c-myc epitopes were inserted yielded twenty-one different derivatives.

Nascent Lep inserts into the Escherichia coli inner membrane in the vicinity of YidC, SecY and SecA.

Targeting and assembly of the Escherichia coli inner membrane protein leader peptidase (Lep) was studied using a homologous in vitro targeting/translocation assay. Assembly of full-length Lep was efficient in the co-translational presence of membrane vesicles and hardly occurred when membranes were added post-translationally. This is consistent with the signal recognition particle-dependent targeting of Lep.

SecA is not required for signal recognition particle-mediated targeting and initial membrane insertion of a nascent inner membrane protein.

In Escherichia coli, signal recognition particle (SRP)-dependent targeting of inner membrane proteins has been described. In vitro cross-linking studies have demonstrated that short nascent chains exposing a highly hydrophobic targeting signal interact with the SRP. This SRP, assisted by its receptor, FtsY, mediates the transfer to a common translocation site in the inner membrane that contains SecA, SecG, and SecY.

Differential use of the signal recognition particle translocase targeting pathway for inner membrane protein assembly in Escherichia coli.

Assembly of several inner membrane proteins-leader peptidase (Lep), a Lep derivative (Lep-inv) that inserts with an inverted topology compared with the wild-type protein, the phage M13 procoat protein, and a procoat derivative (H1-procoat) with the hydrophobic core of the signal peptide replaced by a stretch from the first transmembrane segment in Lep-has been studied in vitro and in Escherichia coli strains that are conditional for the expression of either the 54 homologue (Ffh) or 4.5S RNA, which are the two components of the E. coli signal recognition particle (SRP), or SecE, an essential core component of the E.