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The Outer Membrane Protein Insertion Porin (OmpIP/Omp85) Family [Function: Biogenesis/Secretion] Seed alignment | Full alignment | Pfam Wiki page | TC-DB page

Transmembrane ß-barrels are synthesized in the cytoplasm and transferred through the inner membrane using the Sec system. In the periplasmic space, chaperones such as SurA and Skp, bind these proteins and target them to the outer membrane. It is believed that the highly conserved Omp85 acts in vivo in a way that facilitates the correct folding and the insertion of other &ß-barrels in the outer membrane. The conserved domain in Omp85 is also sometimes referred to as Bacterial Surface Antigen D15 and homologs are also found in mitochondria (Sam50/Tob55) and chloroplasts (OEP75). The transmembrane domain (composed of 16 ß-strands), is located in the C-terminus whereas, in the N-terminus, Omp85 possesses 5 conserved POTRA (Polypeptide Transport) domains. These domains are believed to interact with the transferred &ß-barrel and the final insertion into the outer membrane is performed with lateral diffusion. Conserved motifs that are believed to be parts of the pore-forming region are also found in all members of this family. The SAM complex plays a vital role in the integration of ß barrel proteins into the outer membrane. It consists of SAM50 and two peripheral proteins, SAM35 and SAM37. SAM50 features a single non-membrane polypeptide-transport-associated (POTRA) domain that is not crucial for cell viability and, also, a conserved loop six, which promotes ß-signal binding of the pre-proteins to the lateral gate and insertion of next hairpins into the outer membrane. Biochemical studies revealed that SAM50 has a conserved ß barrel domain -all the way from bacteria to humans. SAM50 forms a 16-strands ß barrel in the mitochondrial outer membrane, which has a N-terminal POTRA domain exposed into the intermembrane space, whereas the bacterial counterparts are known to possess a 16-stranded barrel, information that is experimentally verified since four members of the OmpIP/Omp85 family have experimentally determined 3D. 16 ß strands were also predicted by PRED-TMBB2.


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Literature references


In Situ Labeling and Distance Measurements of Membrane Proteins in E. coli Using Finland and OX063 Trityl Labels
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PMID: 33197077

Mitochondrial sorting and assembly machinery operates by ß-barrel switching
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Structures of the ß-barrel assembly machine recognizing outer membrane protein substrates
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Distortion of the bilayer and dynamics of the BAM complex in lipid nanodiscs
Commun Biol. 2020 Dec 14;3(1):766. doi: 10.1038/s42003-020-01419-w.
PMID: 33318620

Membrane thinning and lateral gating are consistent features of BamA across multiple species
PLoS Comput Biol. 2020 Oct 28;16(10):e1008355. doi: 10.1371/journal.pcbi.1008355. eCollection 2020 Oct.
PMID: 33112853

Functions of the BamBCDE Lipoproteins Revealed by Bypass Mutations in BamA
J Bacteriol. 2020 Oct 8;202(21):e00401-20. doi: 10.1128/JB.00401-20. Print 2020 Oct 8.
PMID: 32817097

SAM50, a side door to the mitochondria: The case of cytotoxic proteases
Pharmacol Res. 2020 Oct;160:105196. doi: 10.1016/j.phrs.2020.105196. Epub 2020 Sep 9.
PMID: 32919042

The gain-of-function allele bamA (E470K) bypasses the essential requirement for BamD in ß-barrel outer membrane protein assembly
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PMID: 32675245

Structural insight into mitochondrial ß-barrel outer membrane protein biogenesis
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PMID: 32620929

Structural insight into the formation of lipoprotein-ß-barrel complexes
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PMID: 32572278

Identification of a Compound That Inhibits the Growth of Gram-Negative Bacteria by Blocking BamA-BamD Interaction
Front Microbiol. 2020 Jun 19;11:1252. doi: 10.3389/fmicb.2020.01252. eCollection 2020.
PMID: 32636816

Structure of a nascent membrane protein as it folds on the BAM complex
Nature. 2020 Jul;583(7816):473-478. doi: 10.1038/s41586-020-2370-1. Epub 2020 Jun 11.
PMID: 32528179

Crystallization and X-ray analysis of Borrelia burgdorferi ß-barrel assembly machinery A
Acta Crystallogr F Struct Biol Commun. 2020 Jun 1;76(Pt 6):235-240. doi: 10.1107/S2053230X20006196. Epub 2020 May 29.
PMID: 32510463

Characterization of BamA reconstituted into a solid-supported lipid bilayer as a platform for measuring dynamics during substrate protein assembly into the membrane
Biochim Biophys Acta Biomembr. 2020 Sep 1;1862(9):183317. doi: 10.1016/j.bbamem.2020.183317. Epub 2020 May 4.
PMID: 32380170

Membrane protein insertion through a mitochondrial ß-barrel gate
Science. 2018 Jan 19;359(6373):eaah6834. doi: 10.1126/science.aah6834.
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Identification of new channels by systematic analysis of the mitochondrial outer membrane
J Cell Biol. 2017 Nov 6;216(11):3485-3495. doi: 10.1083/jcb.201706043. Epub 2017 Sep 15.
PMID: 28916712

Granzyme B enters the mitochondria in a Sam50-, Tim22- and mtHsp70-dependent manner to induce apoptosis
Cell Death Differ. 2017 Apr;24(4):747-758. doi: 10.1038/cdd.2017.3. Epub 2017 Mar 24.
PMID: 28338658

Mitochondrial-bacterial hybrids of BamA/Tob55 suggest variable requirements for the membrane integration of ß-barrel proteins
Sci Rep. 2016 Dec 16;6:39053. doi: 10.1038/srep39053.
PMID: 27982054

Structure of BamA, an essential factor in outer membrane protein biogenesis
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The structural basis of autotransporter translocation by TamA
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PMID: 24056943

Structural insight into the biogenesis of ß-barrel membrane proteins
Nature. 2013 Sep 19;501(7467):385-90. doi: 10.1038/nature12521. Epub 2013 Sep 1.
PMID: 23995689

Characterization of the insertase for ß-barrel proteins of the outer mitochondrial membrane
J Cell Biol. 2012 Nov 12;199(4):599-611. doi: 10.1083/jcb.201207161. Epub 2012 Nov 5.
PMID: 23128244

High-resolution structure of a new crystal form of BamA POTRA4-5 from Escherichia coli
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2011 Jul 1;67(Pt 7):734-8. doi: 10.1107/S1744309111014254. Epub 2011 Jun 23.
PMID: 21795783

Structure and evolution of mitochondrial outer membrane proteins of beta-barrel topology
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Dissecting membrane insertion of mitochondrial beta-barrel proteins
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PMID: 18358813

The peripheral membrane subunits of the SAM complex function codependently in mitochondrial outer membrane biogenesis
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PMID: 17978093

Structure and function of an essential component of the outer membrane protein assembly machine
Science. 2007 Aug 17;317(5840):961-4. doi: 10.1126/science.1143993.
PMID: 17702946

The N-terminal domain of Tob55 has a receptor-like function in the biogenesis of mitochondrial beta-barrel proteins
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PMID: 17190789

Conserved pore-forming regions in polypeptide-transporting proteins
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PMID: 15752354

Biogenesis of the Gram-negative bacterial outer membrane
Curr Opin Microbiol. 2004 Dec;7(6):610-6. doi: 10.1016/j.mib.2004.10.011.
PMID: 15556033

Omp85, an evolutionarily conserved bacterial protein involved in outer-membrane-protein assembly
Res Microbiol. 2004 Apr;155(3):129-35. doi: 10.1016/j.resmic.2003.11.007.
PMID: 15143770

The Omp85 family of proteins is essential for outer membrane biogenesis in mitochondria and bacteria
J Cell Biol. 2004 Jan 5;164(1):19-24. doi: 10.1083/jcb.200310092. Epub 2003 Dec 29.
PMID: 14699090

Evolutionary conservation of biogenesis of beta-barrel membrane proteins
Nature. 2003 Dec 18;426(6968):862-6. doi: 10.1038/nature02208.
PMID: 14685243

An essential role of Sam50 in the protein sorting and assembly machinery of the mitochondrial outer membrane
J Biol Chem. 2003 Dec 5;278(49):48520-3. doi: 10.1074/jbc.C300442200. Epub 2003 Oct 21.
PMID: 14570913

POTRA: a conserved domain in the FtsQ family and a class of beta-barrel outer membrane proteins
Trends Biochem Sci. 2003 Oct;28(10):523-6. doi: 10.1016/j.tibs.2003.08.003.
PMID: 14559180

Proteins in this family with 3D-structure
View Entry
Description
Organism
Length
# strands
Outer membrane protein assembly factor BamA
Neisseria gonorrhoeae (strain ATCC 700825 / FA 1090)
792
16
Outer membrane protein assembly factor BamA
Haemophilus ducreyi
793
16
Outer membrane protein assembly factor BamA
Escherichia coli (strain K12)
810
16
Outer membrane protein assembly factor BamA
Escherichia coli O157:H7
810
16
Outer membrane protein assembly factor BamA
Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720)
804
16
Bac_surface_Ag domain-containing protein
Myceliophthora thermophila (strain ATCC 42464 / BCRC 31852 / DSM 1799)(Sporotrichum thermophile)
512
14


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