PDBsum entry 4xhm

Oxidoreductase

PDB id: 4xhm

Contents

Protein chains

110 a.a.

Waters ×285

PDB id:

4xhm

Name:

Oxidoreductase

Title:

Archaeoglobus fulgidus thioredoxin 3 m60h

Structure:

Thioredoxin (trx-3). Chain: a, b. Engineered: yes. Mutation: yes

Source:

Archaeoglobus fulgidus (strain atcc 49558 / vc- 16 / dsm 4304 / jcm 9628 / nbrc 100126). Organism_taxid: 224325. Strain: atcc 49558 / vc-16 / dsm 4304 / jcm 9628 / nbrc 100126. Gene: af_1284. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.95Å R-factor: 0.194 R-free: 0.250

Authors:

M.Dey,R.E.Bjork,C.L.Drennan

Key ref:

K.D.Bewley et al. (2015). Rheostat re-wired: alternative hypotheses for the control of thioredoxin reduction potentials. Plos One, 10, e0122466. PubMed id: 25874934 DOI: 10.1371/journal.pone.0122466

Date:

05-Jan-15 Release date: 29-Apr-15

Protein chains

O28984  (O28984_ARCFU) -  Thioredoxin (Trx-3) from Archaeoglobus fulgidus (strain ATCC 49558 / DSM 4304 / JCM 9628 / NBRC 100126 / VC-16)

Seq: 134 a.a.

Struc: 110 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1371/journal.pone.0122466

Plos One 10:e0122466 (2015)

PubMed id: 25874934

Rheostat re-wired: alternative hypotheses for the control of thioredoxin reduction potentials.

K.D.Bewley, M.Dey, R.E.Bjork, S.Mitra, S.E.Chobot, C.L.Drennan, S.J.Elliott.

ABSTRACT

Thioredoxins are small soluble proteins that contain a redox-active disulfide (CXXC). These disulfides are tuned to oxidizing or reducing potentials depending on the function of the thioredoxin within the cell. The mechanism by which the potential is tuned has been controversial, with two main hypotheses: first, that redox potential (Em) is specifically governed by a molecular 'rheostat'-the XX amino acids, which influence the Cys pKa values, and thereby, Em; and second, the overall thermodynamics of protein folding stability regulates the potential. Here, we use protein film voltammetry (PFV) to measure the pH dependence of the redox potentials of a series of wild-type and mutant archaeal Trxs, PFV and glutathionine-equilibrium to corroborate the measured potentials, the fluorescence probe BADAN to measure pKa values, guanidinium-based denaturation to measure protein unfolding, and X-ray crystallography to provide a structural basis for our functional analyses. We find that when these archaeal thioredoxins are probed directly using PFV, both the high and low potential thioredoxins display consistent 2H+:2e- coupling over a physiological pH range, in conflict with the conventional 'rheostat' model. Instead, folding measurements reveals an excellent correlation to reduction potentials, supporting the second hypothesis and revealing the molecular mechanism of reduction potential control in the ubiquitous Trx family.