Letunic et al. (2017) Nucleic Acids Res doi: 10.1093/nar/gkx922
Letunic et al. (2020) Nucleic Acids Res doi: 10.1093/nar/gkaa937

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OmpH Outer membrane protein (OmpH-like)

SMART accession number:	SM00935
Description:	This family includes outer membrane proteins such as OmpH among others. Skp (OmpH) has been characterised as a molecular chaperone that interacts with unfolded proteins as they emerge in the periplasm from the Sec translocation machinery (PUBMED:15304217).
Interpro abstract (IPR005632):	The 17kDa protein Skp (also known as OmpH) of Escherichia coli is a homotrimeric periplasmic chaperone for newly synthesised outer-membrane proteins, the X-ray structure of which has been reported at resolutions of 2.35 A and 2.30 A [ (PUBMED:15361861) (PUBMED:15304217) ]. Three hairpin-shaped alpha-helical extensions reach out by approximately 60 A from a trimerisation domain, which is composed of three intersubunit beta-sheets that wind around a central axis. The alpha-helical extensions approach each other at their distal turns, resulting in a fold that resembles a 'three-pronged grasping forcep'. The overall shape of Skp is reminiscent of the cytosolic chaperone prefoldin, although it is based on a radically different topology. The peculiar architecture, with apparent plasticity of the prongs and distinct electrostatic and hydrophobic surface properties, supports the recently proposed biochemical mechanism of this chaperone: formation of a Skp(3)-Omp complex protects the outer membrane protein from aggregation during passage through the bacterial periplasm. The ability of Skp to prevent the aggregation of model substrates in vitro is independent of ATP. Skp can interact directly with membrane lipids and lipopolysaccharide. These interactions are needed for efficient Skp-assisted folding of membrane proteins [ (PUBMED:15304217) ]. The Haemophilus influenzae member of the family, OMP26, is an outer membrane protein that shows significant potential as a vaccine candidate [ (PUBMED:10085039) ]. It is not clear if this protein has undergone adaptive changes in H. influenzae so as to locate to the outer membrane, or if Skp proteins are to some extent peripherally associated with the outer membrane in all species.
GO function:	unfolded protein binding (GO:0051082)
Family alignment:	View or CHROMA formatHMM/Web logoCLUSTALW formatMSF formatFASTA formatPIR format

There are 13114 OmpH domains in 13106 proteins in SMART's nrdb database.

Click on the following links for more information.

• Evolution (species in which this domain is found)

• Taxonomic distribution of proteins containing OmpH domain.

  This tree includes only several representative species. The complete taxonomic breakdown of all proteins with OmpH domain is also avaliable.

  Click on the protein counts, or double click on taxonomic names to display all proteins containing OmpH domain in the selected taxonomic class.

• Cellular role (predicted cellular role)

• Cellular role: interaction
  

• Literature (relevant references for this domain)

• Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

  • Hirvas L, Coleman J, Koski P, Vaara M
  • Bacterial 'histone-like protein I' (HLP-I) is an outer membraneconstituent?
  • FEBS Lett. 1990; 262: 123-6
  • Display abstract

  • The nucleoid-associated 'histone-like protein I' (HLP-I) protein of E.coli was found to be homologous with the cationic 16-kDa outer membraneprotein OmpH of Salmonella typhimurium. Deduced from the nucleotidesequence, the HLP-I protein has 91% identical residues with the OmpHprotein. Both proteins have very similar cleavable signal sequences. Thenucleotide sequence similarity between the corresponding genes hlpA andompH is 87%. The ompH gene is located in a gene cluster resembling thehlpA-ORF17 region of E. coli which is close to the Ipx genes involved inthe biosynthesis of lipopolysaccharides. The localization of theOmpH/HLP-I protein in the cell is discussed.

• Structure (3D structures containing this domain)

• 3D Structures of OmpH domains in PDB

  PDB code	Main view	Title
  1sg2		Crystal structure of the periplasmic chaperone Skp
  1u2m		Crystal Structure of Skp
  4kqt		Crystal structure of a putative outer membrane chaperone (OmpH-like) (CC_1914) from Caulobacter crescentus CB15 at 2.83 A resolution (PSI Community Target, Shapiro)

• Links (links to other resources describing this domain)

• PFAM	OmpH
  INTERPRO	IPR005632

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