PMID:15840585

Citation	Hennecke, G, Nolte, J, Volkmer-Engert, R, Schneider-Mergener, J and Behrens, S (2005) The periplasmic chaperone SurA exploits two features characteristic of integral outer membrane proteins for selective substrate recognition. J. Biol. Chem. 280:23540-8
Abstract	The Escherichia coli periplasmic chaperone and peptidyl-prolyl isomerase (PPIase) SurA facilitates the maturation of outer membrane porins. Although the PPIase activity exhibited by one of its two parvulin-like domains is dispensable for this function, the chaperone activity residing in the non-PPIase regions of SurA, a sizable N-terminal domain and a short C-terminal tail, is essential. Unlike most cytoplasmic chaperones SurA is selective for particular substrates and recognizes outer membrane porins synthesized in vitro much more efficiently than other proteins. Thus, SurA may be specialized for the maturation of outer membrane proteins. We have characterized the substrate specificity of SurA based on its natural, biologically relevant substrates by screening cellulose-bound peptide libraries representing outer membrane proteins. We show that two features are critical for peptide binding by SurA: specific patterns of aromatic residues and the orientation of their side chains, which are found more frequently in integral outer membrane proteins than in other proteins. For the first time this sufficiently explains the capability of SurA to discriminate between outer membrane protein and non-outer membrane protein folding intermediates. Furthermore, peptide binding by SurA requires neither an active PPIase domain nor the presence of proline, indicating that the observed substrate specificity relates to the chaperone function of SurA. Finally, we show that SurA is capable of associating with the outer membrane. Together, our data support a model in which SurA is specialized to interact with non-native periplasmic outer membrane protein folding intermediates and to assist in their maturation from early to late outer membrane-associated steps.
Links	PubMed Online version:10.1074/jbc.M413742200
Keywords	Amino Acid Sequence; Bacterial Outer Membrane Proteins/metabolism; Carrier Proteins/metabolism; Carrier Proteins/physiology; Escherichia coli Proteins/metabolism; Escherichia coli Proteins/physiology; Molecular Chaperones/metabolism; Molecular Chaperones/physiology; Molecular Sequence Data; Peptidylprolyl Isomerase/metabolism; Peptidylprolyl Isomerase/physiology; Periplasm/metabolism; Protein Binding; Substrate Specificity; Surface Plasmon Resonance
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:SURA	enables	GO:0042277: peptide binding	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete

References

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