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

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