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

In mitochondria, chloroplasts, and Gram-negative eubacteria, Oxa1p(-like) proteins are critical for the biogenesis of membrane proteins. Here we show that the Gram-positive eubacterium Bacillus subtilis contains two functional Oxa1p orthologues, denoted SpoIIIJ and YqjG. The presence of either SpoIIIJ or YqjG is required for cell viability. Whereas SpoIIIJ is required for sporulation, YqjG is dispensable for this developmental process. The stability of two membrane proteins was found to be mildly affected upon SpoIIIJ limitation in the absence of YqjG. Surprisingly, the topology and stability of other membrane proteins remained unaffected under these conditions. In contrast, SpoIIIJ-and YqjGlimiting conditions resulted in a strong post-translocational defect in the stability of secretory proteins. Together, these data indicate that SpoIIIJ and YqjG of B. subtilis are involved in both membrane protein biogenesis and protein secretion. However, the reduced stability of secretory proteins seems to be the most prominent phenotype of SpoIIIJ/YqjG-depleted B. subtilis cells. In conclusion, our observations show that SpoIIIJ and YqjG have different, but overlapping functions in B. subtilis. Most importantly, it seems that different members of the Oxa1p protein family have acquired at least partly distinct, species-specific, functions that are essential for life.

Section: Discussionmentioning

confidence: 97%

Complementary Impact of Paralogous Oxa1-like Proteins of Bacillus subtilis on Post-translocational Stages in Protein Secretion

Tjalsma

Bron

Dijl

2003

“…FtsQ is a monotopic membrane protein with an N-terminal transmembrane domain and a large C-terminal periplasmic domain. Previous studies utilized IMVs as target membranes (12,35). However, the reconstitution of such a complex process is an important step toward a detailed understanding of the minimal requirements of membrane protein insertion.…”

Section: Discussionmentioning

confidence: 99%

SecYEG Proteoliposomes Catalyze the Δϕ-Dependent Membrane Insertion of FtsQ

Laan

Nouwen

Driessen

2004

In Escherichia coli, the insertion of most inner membrane proteins is mediated by the Sec translocase. Ribosome-bound nascent chains of Sec-dependent inner membrane proteins are targeted to the SecYEG complex via the signal recognition particle pathway. We now demonstrate that the signal recognition particledependent co-translational membrane targeting and membrane insertion of FtsQ can be reconstituted with proteoliposomes containing purified SecYEG. SecA and a transmembrane electrical potential are essential for the translocation of the large periplasmic domain of FtsQ, whereas co-reconstituted YidC has an inhibitory effect. These data demonstrate that membrane protein insertion can be reconstituted with a minimal set of purified Sec components.

“…Refs. [12][13][14][15]. It has been suggested that YidC mediates the transfer of TMs from the Sec translocon into the lipid bilayer (1).…”

mentioning

confidence: 99%

Biogenesis of MalF and the MalFGK2 Maltose Transport Complex in Escherichia coli Requires YidC

Wagner

Pop

Haan

et al. 2008

Self Cite

The polytopic inner membrane protein MalF is a constituent of the MalFGK 2 maltose transport complex in Escherichia coli. We have studied the biogenesis of MalF using a combination of in vivo and in vitro approaches. MalF is targeted via the SRP pathway to the Sec/YidC insertion site. Despite close proximity of nascent MalF to YidC during insertion, YidC is not required for the insertion of MalF into the membrane. However, YidC is required for the stability of MalF and the formation of the MalFGK 2 maltose transport complex. Our data indicate that YidC supports the folding of MalF into a stable conformation before it is incorporated into the maltose transport complex.