Valence and anion binding of bovine ribonuclease A between pH 6 and 8.
Several studies have shown that divalent anion binding to ribonuclease A (RNase A) contributes to RNase A folding and stability. However, there are conflicting reports about whether chloride binds to or stabilizes RNase A. Two broad-zone experimental approaches, membrane-confined electrophoresis and analytical ultracentrifugation, were used to examine the electrostatic and electrohydrodynamic characteristics of aqueous solutions of bovine RNase A in the presence of 100 mM KCl and 10 mM Bis-Tris propane over a pH range of 6.00-8.00. The results of data analysis using a Debye-Huckel-Henry model, compared with expectations based on pK(A) values, are consistent with the binding of two chlorides by RNase A. The decreased protein valence resulting from anion binding contributes 2-3 kJ/mol to protein stabilization. This work demonstrates the utility of first-principle valence determinations to detect protein solution properties that might otherwise remain undetected.
Moody
Thomas P
TP
Center to Advance Molecular Interaction Science, Rudman Hall, 46 College Road, University of New Hampshire, Durham, NH 03824, USA. tpm@cisunix.unh.edu
Kingsbury
Jonathan S
JS
Durant
Jennifer A
JA
Wilson
Timothy J
TJ
Chase
Susan F
SF
Laue
Thomas M
TM
D000818:Animals; D000838:Anions / Q000737:chemistry* / Q000378:metabolism*; D002417:Cattle; D004563:Electrochemistry; D004586:Electrophoresis; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D012259:Ribonuclease, Pancreatic / Q000737:chemistry* / Q000378:metabolism*; D012996:Solutions / Q000737:chemistry; D055672:Static Electricity
D000838:Anions; D012996:Solutions; D012259:Ribonuclease, Pancreatic