Replacement of proline-76 with alanine eliminates the slowest kinetic phase in thioredoxin folding.


Abstract

The conformational transition observed upon addition of guanidine hydrochloride (Gdn-HCl) to solutions of oxidized Escherichia coli thioredoxin is dominated by a slow kinetic phase (time constant tau 1 = 300-800 s) that has features appropriate to a proline peptide isomerization. This observation has been interpreted as reflecting a folding pathway involving an obligatory isomerization of the imide peptide bond between isoleucine-75 and proline-76 [Kelley, R. F., & Stellwagen, E. (1984) Biochemistry 23, 5095-5102]; this peptide bond is known to have the cis configuration in the folded state [Eklund, H., Cambillan, C., Sjöberg, B.-M., Holmgren, A., Jörnvall, H., Höög, J.-O., & Brändén, C.-I. (1984) EMBO J. 3, 1443-1449]. We have tested this hypothesis by examining the conformational transitions of two thioredoxin mutants, trxA76 having an alanine substituted for proline-76 and trxA2 [Russel, M., & Model, P. (1983) J. Bacteriol. 154, 1064-1070] having proline-34 replaced with serine. Both mutant proteins display far-ultraviolet circular dichroic spectra similar to that of native wild-type thioredoxin. The tryptophan fluorescence emission of native trxA2 is equivalent to that of wild-type thioredoxin, while the emission intensity of native trxA76 at 350 nm is 2-fold greater. Tryptophan fluorescence and peptide ellipticity measurements indicate that the mutant proteins undergo two-state and reversible equilibrium unfolding transitions upon addition of guanidine hydrochloride (Gdn-HCl). These transitions are centered at 2.4 and 1.5 M Gdn-HCl for trxA2 and trxA76, respectively, as compared to a midpoint of 2.5 M denaturant for wild-type thioredoxin. As observed for wild-type thioredoxin, fluorescence measurements reveal monophasic unfolding kinetics for trxA2 at a variety of final denaturant concentrations. The tau for unfolding varies monotonically from 210 s in 2.4 M Gdn-HCl to 7 s for a final Gdn-HCl concentration of 3.5 M. Refolding of denatured trxA2 in 1.5 M Gdn-HCl detected by fluorescence measurements is described by three kinetic phases with time constants and fractional amplitudes (alpha) similar to those of wild-type thioredoxins. The fractional amplitude (alpha 1) of the slowest of these phases, tau 1 = 430 +/- 38 s in 2.0 M Gdn-HCl, decreases with final Gdn-HCl concentration. Multimixing experiments suggest that this phase results from an equilibration between denatured forms and has a tau of 34 s in 4 M denaturant, features previously observed for the wild-type protein.(ABSTRACT TRUNCATED AT 400 WORDS) Study holds ProTherm entries: 3923, 3924, 3925 Extra Details: slow kinetic phase; proline peptide isomerization;,folding pathway; folded intermediate

Submission Details

ID: 5Bzw5ucf3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:23 p.m.

Version: 1

Publication Details
Kelley RF;Richards FM,Biochemistry (1987) Replacement of proline-76 with alanine eliminates the slowest kinetic phase in thioredoxin folding. PMID:3322388
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
3DXB 2008-07-24T00:00:00+0000 2.2 Structure of the UHM domain of Puf60 fused to thioredoxin
5E4W 2015-10-07T00:00:00+0000 2.8 Crystal structure of cpSRP43 chromodomains 2 and 3 in complex with the Alb3 tail
5IKN 2016-03-03T00:00:00+0000 4.8 Crystal Structure of the T7 Replisome in the Absence of DNA
1F6M 2000-06-22T00:00:00+0000 2.95 CRYSTAL STRUCTURE OF A COMPLEX BETWEEN THIOREDOXIN REDUCTASE, THIOREDOXIN, AND THE NADP+ ANALOG, AADP+
1KEB 2001-11-15T00:00:00+0000 1.8 Crystal Structure of Double Mutant M37L,P40S E.coli Thioredoxin
1M7T 2002-07-22T00:00:00+0000 0 Solution Structure and Dynamics of the Human-Escherichia coli Thioredoxin Chimera: Insights into Thermodynamic Stability
1OAZ 2003-01-21T00:00:00+0000 2.78 IgE Fv SPE7 complexed with a recombinant thioredoxin
1SKR 2004-03-05T00:00:00+0000 2.4 T7 DNA Polymerase Complexed To DNA Primer/Template and ddATP
1SKS 2004-03-05T00:00:00+0000 2.3 Binary 3' complex of T7 DNA polymerase with a DNA primer/template containing a cis-syn thymine dimer on the template
1SKW 2004-03-05T00:00:00+0000 2.3 Binary 3' complex of T7 DNA polymerase with a DNA primer/template containing a disordered cis-syn thymine dimer on the template

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Thioredoxin 1 P0AA27 THIO_ECO57
100.0 Thioredoxin 1 P0AA26 THIO_ECOL6
100.0 Thioredoxin 1 P0AA25 THIO_ECOLI
100.0 Thioredoxin 1 P0AA29 THIO_SALTI
100.0 Thioredoxin 1 P0AA28 THIO_SALTY
100.0 Thioredoxin 1 P0AA30 THIO_SHIFL