Thurkill2006_pKa - Downloaded from www.proteinscience.org on September 6 2008 Published by Cold Spring Harbor Laboratory Press pK values of the

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10.1110/ps.051840806 Access the most recent version at doi: 2006 15: 1214-1218; originally published online Apr 5, 2006; Protein Sci. Richard L. Thurlkill, Gerald R. Grimsley, J. Martin Scholtz and C. Nick Pace pK values of the ionizable groups of proteins References http://www.proteinscience.org/cgi/content/full/15/5/1214#otherarticles Article cited in: http://www.proteinscience.org/cgi/content/full/15/5/1214#References This article cites 46 articles, 10 of which can be accessed free at: service Email alerting click here top right corner of the article or Receive free email alerts when new articles cite this article - sign up in the box at the Notes http://www.proteinscience.org/subscriptions/ go to: Protein Science To subscribe to © 2006 Cold Spring Harbor Laboratory Press Cold Spring Harbor Laboratory Press on September 6, 2008 - Published by www.proteinscience.org Downloaded from
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FOR THE RECORD pK values of the ionizable groups of proteins RICHARD L. THURLKILL, 1,2,3 GERALD R. GRIMSLEY, 1 J. MARTIN SCHOLTZ, 1,2 AND C. NICK PACE 1,2 1 College Station, Texas 77843, USA 2 (R ECEIVED November 17, 2005; F INAL R EVISION January 18, 2006; A CCEPTED January 18, 2006) Abstract We have used potentiometric titrations to measure the pK values of the ionizable groups of proteins in alanine pentapeptides with appropriately blocked termini. These pentapeptides provide an improved model for the pK values of the ionizable groups in proteins. Our pK values determined in 0.1 M KCl at 25 ° Care:3.67 6 0.03 ( a -carboxyl), 3.67 6 0.04 (Asp), 4.25 6 0.05 (Glu), 6.54 6 0.04 (His), 8.00 6 0.03 ( a -amino), 8.55 6 0.03 (Cys), 9.84 6 0.11 (Tyr), and 10.40 6 0.08 (Lys). The pK values of some groups 4.0 N&T); His (6.54 this work vs. 6.3 N&T); a -amino (8.00 this work vs. 7.5 N&T); Cys (8.55 this work vs. 9.5 N&T); perturbations in folded and unfolded proteins, and to those who use theory to gain a better understanding of the factors that determine the pK values of the ionizable groups of proteins. Keywords: pK values; protein ionizable groups; pH titration; peptide model compounds The acid/base properties of proteins have been studied since 1917, when Sorensen, who first defined pH in 1909, showed that egg albumin is an ampholyte (Sorensen et al. 1917). Soon thereafter, Linderstrom-Lang recognized that the net charge on a protein would influence the ionization of individual groups, and incorporated this into the first model developed to understand the acid/base properties of a protein (Linderstrom-Lang 1924). An important contri- bution by Tanford and Kirkwood triggered an intense interest
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This note was uploaded on 05/28/2010 for the course WE BIBI010000 taught by Professor Marnikvuylsteke during the Spring '10 term at Ghent University.

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Thurkill2006_pKa - Downloaded from www.proteinscience.org on September 6 2008 Published by Cold Spring Harbor Laboratory Press pK values of the

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