title: Effect of electrostatic interactions on the binding of charged substrate to GroEL studied by highly sensitive fluorescence correlation spectroscopy.
abstract: The binding processes of GroEL with apo cytochrome c (apo-cyt c) and disulfide-reduced apo alpha-lactalbumin (rLA) in homogeneous solution at low concentration were analyzed by fluorescence correlation spectroscopy (FCS) with extremely high sensitivity. Although apo-cyt c, a positively charged substrate, was tightly bound to GroEL in both the absence and the presence of 200 mM KCl, the strength of the binding was changed with varying salt concentration. Results from experiments when two different salts (KCl or MgCl(2)) were titrated into a sample solution containing GroEL and apo-cyt c clearly showed that the binding strength decreased with increasing salt concentration. On the other hand, the binding affinity of GroEL for rLA, a negatively charged substrate, increased by adding of 200 mM KCl. These results indicate that electrostatic interactions substantially contribute to the binding interactions by manipulating the binding affinity of charged substrates.
authors.affiliation: Research Institute for Electronic Science, Hokkaido University, N12W6, Kita-ku, Sapporo, 060-0812, Japan. cback@imd.es.hokudai.ac.jp
authors.forename: C G
authors.initials: CG
authors.lastname: Pack
authors.forename: K
authors.initials: K
authors.lastname: Aoki
authors.forename: H
authors.initials: H
authors.lastname: Taguchi
authors.forename: M
authors.initials: M
authors.lastname: Yoshida
authors.forename: M
authors.initials: M
authors.lastname: Kinjo
authors.forename: M
authors.initials: M
authors.lastname: Tamura
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018834:Chaperonin 60 / Q000737:chemistry* / Q000378:metabolism*; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism; D045304:Cytochromes c; D006736:Horses; D007700:Kinetics; D007768:Lactalbumin / Q000737:chemistry* / Q000378:metabolism; D009994:Osmolar Concentration; D011189:Potassium Chloride; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000379:methods; D055672:Static Electricity
chemical_list: D001059:Apoproteins; D018834:Chaperonin 60; D003574:Cytochrome c Group; C041966:apo-alpha-lactalbumin; D011189:Potassium Chloride; D045304:Cytochromes c; D007768:Lactalbumin