The effect of net charge on the solubility, activity, and stability of ribonuclease Sa

Citation
Kl. Shaw et al., The effect of net charge on the solubility, activity, and stability of ribonuclease Sa, PROTEIN SCI, 10(6), 2001, pp. 1206-1215
Citations number
65
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
PROTEIN SCIENCE
ISSN journal
0961-8368 → ACNP
Volume
10
Issue
6
Year of publication
2001
Pages
1206 - 1215
Database
ISI
SICI code
0961-8368(200106)10:6<1206:TEONCO>2.0.ZU;2-U
Abstract
The net charge and isoelectric pH (pI) of a protein depend on the content o f ionizable groups and their pK values. Ribonuclease Sa (RNase Sa) is an ac idic protein with a pI = 3.5 that contains no Lys residues. By replacing As p and Glu residues on the surface of RNase Sa with Lys residues: we have cr eated a 3K variant (D1K, D17K, E41K) with a pI = 6.4 and a 5K variant (3K D25K, E74K) with a pI = 10.2. We show that pi values estimated using pK va lues based on model compound data can be in error by >1 pH unit, and sugges t how the estimation can be improved. For RNase Sa and the 3K and 5K varian ts, the solubility, activity, and stability have been measured as a functio n of pH. We find that the pH of minimum solubility varies with the pi of th e protein, but that the pH of maximum activity and the pH of maximum stabil ity do not.