Evidence for conservation of architecture and physical properties of Omp85-like proteins throughout evolution

Surana, Neeraj K.; Grass, Susan; Hardy, Gail G.; H, Li; Thanassi, David G.; Geme, Joseph W. St.

doi:10.1073/pnas.0404679101

Cited by 55 publications

(74 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For instance, nOmp85 forms complexes with a putative trimeric structure (Fig. 1) similar to that of other known PTBs from proteobacteria (23,38). We have shown that the N-terminal domain is required for the complex formation in vitro (Fig.…”

Section: Relationship Between Prokaryotic and Eukaryotic Members Of Tmentioning

confidence: 87%

Functional and Phylogenetic Properties of the Pore-forming β-Barrel Transporters of the Omp85 Family

Bredemeier

Schlegel

Ertel

et al. 2007

Journal of Biological Chemistry

101

View full text Add to dashboard Cite

␤-Barrel-shaped channels of the Omp85 family are involved in the translocation or assembly of proteins of bacterial, mitochondrial, and plastidic outer membranes. We have compared these proteins to understand the evolutionary development of the translocators. We have demonstrated that the proteins from proteobacteria and mitochondria have a pore diameter that is at least five times smaller than found for the Omp85 in cyanobacteria and plastids. This finding can explain why Omp85 from cyanobacteria (but not the homologous protein from proteobacteria) was remodeled to become the protein translocation pore after endosymbiosis. Further, the pore-forming region of the Omp85 proteins is restricted to the C terminus. Based on a phylogenetic analysis we have shown that the pore-forming domain displays a different evolutionary relationship than the N-terminal domain. In line with this, the affinity of the N-terminal domain to the C-terminal region of the Omp85 from plastids and cyanobacteria differs, even though the N-terminal domain is involved in gating of the pore in both groups. We have further shown that the N-terminal domain of nOmp85 takes part in homo-oligomerization. Thereby, the differences in the phylogeny of the two domains are explained by different functional constraints acting on the regions. The poreforming domain, however, is further divided into two functional regions, where the distal C terminus itself forms a dimeric pore. Based on functional and phylogenetic analysis, we suggest an evolutionary scenario that explains the origin of the contemporary translocon.Polypeptide transport and assembly of proteins into or across the outer membrane of endosymbiotic organelles or Gram-negative bacteria depend on ␤-barrel-shaped channels (1-4). One class of these proteins is composed of polypeptide-transporting ␤-barrel (PTB) 6 channels, whose topology was determined by modeling (5-7). PTBs of recent interest are, e.g. outer membrane proteins (which secrete adhesins such as hemagglutinin) (8, 9) and bacterial (1, 7, 10 -12), mitochondrial (Tob55/Sam50) (5, 13, 14), and chloroplast outer membrane proteins (Toc75) (15) of the Omp85 family. The PTBs are partitioned into two functional categories, namely in translocation of precursor proteins across the membrane and in the assembly of outer membrane proteins (3). Furthermore, comparison between chloroplastic, mitochondrial, and bacterial Omp85 protein sequences revealed a high similarity of these PTBs (14,16,17).The PTB Toc75 forms a complex with Toc34, Toc64, and Toc159 (3). A precursor protein-binding site at Toc75 (15, 18), together with the action of Toc159 (19), facilitates the translocation of precursor proteins across the membrane. In contrast, the Omp85 proteins from Neisseria meningitidis, Escherichia coli, and mitochondria are involved in the assembly of outer membrane proteins (1,5,7,(11)(12)(13)(14). As found for Toc75, the mitochondrial PTB is a component of a larger complex with Mas37 (20, 13) and Tob38/Sam35 (21,22).Recently, it was demonstrated that t...

show abstract

Section: Relationship Between Prokaryotic and Eukaryotic Members Of Tmentioning

confidence: 87%

Functional and Phylogenetic Properties of the Pore-forming β-Barrel Transporters of the Omp85 Family

Bredemeier

Schlegel

Ertel

et al. 2007

Journal of Biological Chemistry

101

View full text Add to dashboard Cite

show abstract

“…In fact, in both the channel and concerted model the later stages of translocation such as the dissociation of Hbp from BamA are difficult to reconcile with a monomeric BamA. Interestingly, BamA and BamA-like proteins have been shown to oligomerize in vitro (Paschen et al, 2003;Robert et al, 2006;Surana et al, 2004), suggesting the existence of a hydrophobic central cavity as an insertion site for OMPs docked to the Bam complex by SurA. The binding of SurA could then trigger conformational changes of the Bam complex to accommodate an 'expanded', loosely folded bbarrel in that hydrophobic core.…”

Section: Discussionmentioning

confidence: 99%

The Bam (Omp85) complex is involved in secretion of the autotransporter haemoglobin protease

et al. 2009

View full text Add to dashboard Cite

Autotransporters are large virulence factors secreted by Gram-negative bacteria. They are synthesized with a C-terminal domain that forms a b-barrel pore in the outer membrane implicated in translocation of the upstream 'passenger' domain across the outer membrane. However, recent structural data suggest that the diameter of the b-barrel pore is not sufficient to allow the passage of partly folded structures observed for several autotransporters. Here, we have used a stalled translocation intermediate of the autotransporter Hbp to identify components involved in insertion and translocation of the protein across the outer membrane. At this intermediate stage the b-domain was not inserted and folded as an integral b-barrel in the outer membrane whereas part of the passenger was surface exposed. The intermediate was copurified with the periplasmic chaperone SurA and subunits of the Bam (Omp85) complex that catalyse the insertion and assembly of outer-membrane proteins. The data suggest a critical role for this general machinery in the translocation of autotransporters across the outer membrane.

show abstract

“…The measurement of the swelling rate performed with a range of different size sugars gave an estimation of the size of the pore around 2.7 nm. The specific activities are much lower than for OmpF, suggesting that the pores are either of smaller size than the general diffusion porins (which is unlikely based on the estimated pore size) or remain mainly closed (21). The integrity of the periplasmic domain was shown to be essential for secretion, and thus this region is postulated to participate in substrate recognition and/or interaction (20).…”

mentioning

confidence: 99%

“…By using epitope tagging and accessibility to engineered cysteines, St. Geme and co-workers (21) showed that the N terminus is surface-exposed and followed by a large periplasmic domain and then finally by a C-terminal domain consisting of a ␤-barrel with 10 -13 transmembrane ␤ strands. Liposome swelling assays suggested that HMW1B and the C-terminal domain have pore forming activity.…”

mentioning

confidence: 99%

The TpsB Translocator HMW1B of Haemophilus influenzae Forms a Large Conductance Channel

Duret

Szymanski

Choi

et al. 2008

Journal of Biological Chemistry

View full text Add to dashboard Cite

The Haemophilus influenzae HMW1 adhesin is secreted via the two-partner secretion pathway and requires HMW1B for translocation across the outer membrane. HMW1B belongs to the Omp85-TpsB superfamily of transporters and consists of two structural domains, a C-terminal transmembrane ␤-barrel and an N-terminal periplasmic domain. We investigated the electrophysiological properties of the purified full-length HMW1B and the C-terminal domain using planar lipid bilayers. Both the full-length and the truncated proteins formed conductive pores with a low open probability, two well defined conductance states, and other substates. The kinetic patterns of the two conductance states were distinct, with rapid and frequent transitions to the small conductance state and occasional and more prolonged openings to the large conductance state. The channel formed by the full-length HMW1B showed selectivity for cations, which decreased when measured at pH 5.2, suggesting the presence of acidic residues in the pore. The C-terminal domain of HMW1B was less stable and required reconstitution into liposomes prior to insertion in the bilayer. It formed a channel of smaller conductance but a similar gating pattern as the full-length protein, demonstrating the ability of the last 312 C-terminal amino acids to form a pore and suggesting that the periplasmic domain is not involved in occluding the pore, nor in controlling the inherent basal kinetics of the channel. The HMW1 pro-piece containing the secretion domain, although binding to the channel with high affinity, did not induce channel opening.Secretion of proteins in the external medium from the cytosol of a Gram-negative bacterium is a complex mechanism. Because of the compartmented structure of the cell envelope, a periplasm limited by the inner membrane and the outer membrane, secreted proteins may need to undergo two translocation processes. Seven main types of mechanisms exist to translocate proteins through the cell envelope (1-6). Some of these pathways export the protein directly from the cytosol to the extracellular milieu, whereas others include a periplasmic intermediate step. In this case, independent translocation pathways exist through the inner membrane and comprise the Sec pathway and the TAT pathway (7). The type V secretion pathway is one of those two-step processes, where proteins are first exported to the periplasm in a Sec-dependent manner (5). The second step involves the translocation through the outer membrane of a passenger peptide through a transporter. In many cases, the passenger and the transporter domains belong to the same polypeptide, thus defining an auto-transporter type of mechanism. The two-partner secretion pathway is distinct in that the secreted exoprotein (TpsA) and its cognate transporter protein (TpsB) are translated as two separate proteins but are coded on the same operon or the same locus. Each TpsB transporter is devoted to the translocation of one specific TpsA. For example, the Haemophilus influenzae HMW1/HMW1B pair represents a prototype t...

show abstract

Evidence for conservation of architecture and physical properties of Omp85-like proteins throughout evolution

Cited by 55 publications

References 47 publications

Functional and Phylogenetic Properties of the Pore-forming β-Barrel Transporters of the Omp85 Family

Functional and Phylogenetic Properties of the Pore-forming β-Barrel Transporters of the Omp85 Family

The Bam (Omp85) complex is involved in secretion of the autotransporter haemoglobin protease

The TpsB Translocator HMW1B of Haemophilus influenzae Forms a Large Conductance Channel

Contact Info

Product

Resources

About