title: A summary of the measured pK values of the ionizable groups in folded proteins.
abstract: We tabulated 541 measured pK values reported in the literature for the Asp, Glu, His, Cys, Tyr, and Lys side chains, and the C and N termini of 78 folded proteins. The majority of these values are for the Asp, Glu, and His side chains. The average pK values are Asp 3.5 +/- 1.2 (139); Glu 4.2 +/- 0.9 (153); His 6.6 +/- 1.0 (131); Cys 6.8 +/- 2.7 (25); Tyr 10.3 +/- 1.2 (20); Lys 10.5 +/- 1.1 (35); C-terminus 3.3 +/- 0.8 (22) and N-terminus 7.7 +/- 0.5 (16). We compare these results with the measured pK values of these groups in alanine pentapeptides, and comment on our overall findings.
authors.affiliation: Department of Molecular and Cellular Medicine, Texas A&M University System Health Science Center, College Station, Texas 77843, USA.
authors.forename: Gerald R
authors.initials: GR
authors.lastname: Grimsley
authors.forename: J Martin
authors.initials: JM
authors.lastname: Scholtz
authors.forename: C Nick
authors.initials: CN
authors.lastname: Pace
mesh_terms: D000595:Amino Acid Sequence / Q000502:physiology*; D000596:Amino Acids / Q000737:chemistry*; D001224:Aspartic Acid / Q000737:chemistry; D018698:Glutamic Acid / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D017434:Protein Structure, Tertiary / Q000502:physiology*; D011506:Proteins / Q000737:chemistry*; D017186:Titrimetry
chemical_list: D000596:Amino Acids; D011506:Proteins; D001224:Aspartic Acid; D018698:Glutamic Acid; D006639:Histidine