Analysis of the pH-dependent folding and stability of histidine point mutants allows characterization of the denatured state and transition state for protein folding.


Abstract

pH-Dependent studies of the folding kinetics and stability of a set of His to Gln point mutants were used to characterize the denatured state and transition state ensembles for the C-terminal domain of the ribosomal protein L9 (CTL9). CTL9 contains three histidine residues, two of which, H106 and H134, are buried in the native state, while the third, H144, is more exposed. Comparison of the pH-dependent stability calculated using the Tanford-Wyman linkage relationship to the measured values demonstrates that the apparent pK(a) values of the three histidine residues are not significantly perturbed in the denatured state ensemble. Kinetic measurements show that mutation of H134 has a larger effect on the folding process than does mutation of H106 and H144. The Phi-value for H134 is significantly larger than the Phi-values for the other histidine residues, which are near zero at both pH 5.45 and pH 8.0. The Phi-value for H134 is higher, 0.55, at pH 8.0 than at pH 5.45, 0.39. At pH 5.45, H134 is protonated in the unfolded state but deprotonated in the native state, while at pH 8.0 it is deprotonated in both. There is an excellent linear relationship between stability (logK) and folding rates (logk(f)) over the range of pH 5-9 for all mutants. From these plots, the ratio of DeltaQ( not equal)/DeltaQ can be calculated for each mutant. DeltaQ( not equal) is the difference in the number of protons bound to the transition state and to the unfolded state, while DeltaQ represents the difference between folded and denatured state. The linear plots indicate that the relative position of the transition state ensemble as judged by DeltaQ( not equal)/DeltaQ is independent of pH. The linkage analysis is consistent with the Phi-value analysis, showing that H134 is the most critical contributor to the development of pH-dependent interactions, including desolvation effects in the transition state ensemble. Study holds ProTherm entries: 18499, 18500, 18501, 18502, 18503, 18504, 18505, 18506, 18507, 18508, 18509, 18510, 18511, 18512, 18513, 18514 Extra Details: pD values corrected. Deuterated urea was used. protein folding; protein stability; phi-values; linkage relationship; ribosomal protein L9

Submission Details

ID: WxRC7J454

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:50 p.m.

Version: 1

Publication Details
Horng JC;Cho JH;Raleigh DP,J. Mol. Biol. (2005) Analysis of the pH-dependent folding and stability of histidine point mutants allows characterization of the denatured state and transition state for protein folding. PMID:15567419
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P
 

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)


Relevant PDB Entries

Structure ID Release Date Resolution Structure Title
1CQU 2002-04-27 SOLUTION STRUCTURE OF THE N-TERMINAL DOMAIN OF RIBOSOMAL PROTEIN L9
2HBA 2007-05-29 1.25 Crystal Structure of N-terminal Domain of Ribosomal Protein L9 (NTL9) K12M
2HVF 2007-06-12 1.57 Crystal Structure of N-terminal Domain of Ribosomal Protein L9 (NTL9), G34dA
2HBB 2007-05-29 1.9 Crystal Structure of the N-terminal Domain of Ribosomal Protein L9 (NTL9)
1DIV 1997-01-11 2.6 RIBOSOMAL PROTEIN L9
487D 2000-04-10 7.5 SEVEN RIBOSOMAL PROTEINS FITTED TO A CRYO-ELECTRON MICROSCOPIC MAP OF THE LARGE 50S SUBUNIT AT 7.5 ANGSTROMS RESOLUTION

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
95.3 50S ribosomal protein L9 Q5KU74 RL9_GEOKA
96.6 50S ribosomal protein L9 A4ITV1 RL9_GEOTN
100.0 50S ribosomal protein L9 P02417 RL9_GEOSE