title: Skp Trimer Formation Is Insensitive to Salts in the Physiological Range.
abstract: Biogenesis of the Gram-negative outer membrane involves the chaperone seventeen kilodalton protein (Skp). A Skp trimer is currently thought to bind its unfolded outer membrane protein (uOMP) substrates. Using sedimentation equilibrium, we discovered that Skp is not an obligate trimer under physiological conditions and that Na(+), Cl(-), Mg(2+), and PO4(3-) ions are not linked to Skp trimerization. These findings suggest that electrostatics play a negligible role in Skp assembly. Our results demonstrate that Skp monomers are populated at biologically relevant concentrations, which raises the idea that kinetic formation of Skp-uOMP complexes likely involves Skp monomer assembly around its substrate. In addition, van't Hoff analysis of Skp self-association does not support a previously proposed coupled folding and trimerization of Skp.
authors.affiliation: T. C. Jenkins Department of Biophysics, The Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Clifford W
authors.initials: CW
authors.lastname: Sandlin
authors.affiliation: T. C. Jenkins Department of Biophysics, The Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Zaccai
authors.affiliation: T. C. Jenkins Department of Biophysics, The Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Karen G
authors.initials: KG
authors.lastname: Fleming
mesh_terms: D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D017510:Protein Folding; D055503:Protein Multimerization; D012492:Salts / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D012492:Salts; C072721:Skp protein, E coli