title: The type III secretion chaperone SycE promotes a localized disorder-to-order transition in the natively unfolded effector YopE.
abstract: Many virulence-related, bacterial effector proteins are translocated directly into the cytosol of host cells by the type III secretion (TTS) system. Translocation of most TTS effectors requires binding by specific chaperones in the bacterial cytosol, although how chaperones promote translocation is unclear. To provide insight into the action of such chaperones, we studied the consequences of binding by the Yersinia chaperone SycE to the effector YopE by NMR. These studies examined the intact form of the effector, whereas prior studies have been limited to well ordered fragments. We found that YopE had the characteristics of a natively unfolded protein, with its N-terminal 100 residues, including its chaperone-binding (Cb) region, flexible and disordered in the absence of SycE. SycE binding caused a pronounced disorder-to-order transition in the Cb region of YopE. The effect of SycE was strictly localized to the Cb region, with other portions of YopE being unperturbed. These results provide stringent limits on models of chaperone action and are consistent with the chaperone promoting formation of a three-dimensional targeting signal in the Cb region of the effector. The target of this putative signal is unknown but appears to be a bacterial component other than the TTS ATPase YscN.
authors.affiliation: Section of Molecular Biology, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
authors.forename: Loren
authors.initials: L
authors.lastname: Rodgers
authors.forename: Alicia
authors.initials: A
authors.lastname: Gamez
authors.forename: Roland
authors.initials: R
authors.lastname: Riek
authors.forename: Partho
authors.initials: P
authors.lastname: Ghosh
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D001426:Bacterial Proteins / Q000378:metabolism*; D001692:Biological Transport; D019921:Biotinylation; D002352:Carrier Proteins / Q000378:metabolism*; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000378:metabolism; D008968:Molecular Conformation; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D015534:Trans-Activators / Q000378:metabolism*; D015007:Yersinia / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D018832:Molecular Chaperones; C081269:SycE protein, Yersinia; D015534:Trans-Activators; C063239:yopE protein, Yersinia; D000251:Adenosine Triphosphatases; C086388:YscN protein, Yersinia