Analysis of interaction between chaperonin GroEL and its substrate using fluorescence correlation spectroscopy

✍ Scribed by Chan-Gi Pack; Goro Nishimura; Mamoru Tamura; Katsuhiko Aoki; Hideki Taguchi; Masasuke Yoshida; Masataka Kinjo

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 127 KB
• Volume: 36
• Category: Article
• ISSN: 0196-4763
• DOI: 10.1002/(sici)1097-0320(19990701)36:3<247::aid-cyto15>3.0.co;2-#

✦ Synopsis

Fluorescence correlation spectroscopy (FCS) provides information about translational diffusion properties of fluorescent molecules in tiny detection volume and allows the analysis of binding processes of biomolecules in homogeneous solution. In this study, FCS was used to measure equilibrium binding constants of disulfidereduced apo-␣-lactalbumin (rLA), denatured pepsin, and apo-cytochrome c (apo-cyt c) bound by chaperonin GroEL at different salt concentrations. The results indicate that apo-cyt-c has a much stronger affinity to GroEL than denatured pepsin and rLA have. Titration experiments of GroEL to each substrate with various concentrations of four kinds of salts (K ϩ , Na ϩ , Ca 2ϩ , and Mg 2ϩ ) show that the binding constant of denatured pepsin and rLA to GroEL depends on the salt concentration. The dependence of denatured pepsin binding to GroEL on salt concentration is much stronger than that of rLA. However, the interaction of positively charged apo-cyt c with GroEL is not affected by the salt concentration. Furthermore, the divalent cation promotes the binding of GroEL to denatured pepsin and rLA more strongly than does the monovalent cation.