Thermodynamic characterization of ethidium bromide binding to a unique site on a yeast tRNAPhe

✍ Scribed by Thomas W. Sturgill

• Publisher: Wiley (John Wiley & Sons)
• Year: 1978
• Tongue: English
• Weight: 933 KB
• Volume: 17
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1978.360170713

✦ Synopsis

Abstract

A self‐consistent thermodynamic characterization of the binding of ethidium to yeast phenylalanine‐specific tRNA at 25°C, pH 7.0, in 11 n__M__ MgCl~2~, 375 n__M__ NaCl, and 25 m__M__ sodium phosphate has been obtained. Two ethidium molecules bind per tRNA under these conditions. The stronger site has a dissociation constant equal to 1.9 ± 0.5 μ__M__ and Δ__H__~dis~°′ = 12 ± 1 Kcal/mol, and the weaker sites has a dissociation constant equal to 24 ± 9 μ__M__ and Δ__H__~dis~°′ = 8.9 ± 1.5 Kcal/mol. The average calorimetric Δ__H__~dis~°′ for the to sites 10.6 ± 0.4 kcal/mol. The thermodynamics of binding to the stranger sites are most probably the thermodynamics of interaction between A·U (6) and A·U (7), the unique site identified by Jones and Kearns. The binding is enthalpically driven and classical hydrophobic interactions do not appear to be important in the binding reaction.