Open AccessNMR solution structure of a novel thioredoxin from Bacillus acidocaldarius
Author(s) -
Nicastro Giuseppe,
de Chiara Cesira,
Pedone Emilia,
Tatò Marco,
Rossi Mosè,
Bartolucci Simonetta
Publication year - 2000
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2000.01015.x
Subject(s) - thioredoxin , thermostability , crystallography , dihedral angle , hydrogen bond , chemistry , escherichia coli , molecular dynamics , ionic bonding , molecule , biochemistry , computational chemistry , enzyme , ion , organic chemistry , gene
The thioredoxin (Trx) from Bacillus acidocaldarius (BacTrx), an eubacterium growing optimally at 333 K, is the first Trx described to date from a moderate thermophilic source. To understand the molecular basis of its thermostability, the three‐dimensional structure in the oxidized form was determined by NMR methods. A total of 2276 1 H‐NMR derived distance constraints along with 23 hydrogen‐bonds, 72 φ and 27 χ 1 torsion angle restraints, were used in a protocol employing simulated annealing followed by restrained molecular dynamics and restrained energy minimization. BacTrx consists of a well‐defined core region of five strands of β‐sheet, surrounded by four exposed α‐helices, features shared by other members of the thioredoxin family. The BacTrx 3D structure was compared with the Escherichia coli Trx (EcTrx) determined by X‐ray crystallographic diffraction, and a number of structural differences were observed that may contribute to its thermostabilty. The results of structural analysis indicated that protein stability is due to cumulative effects, the main factor being an increased number of ionic interactions cross‐linking different secondary structural elements and clamping the C‐terminal α‐helix to the core of the protein.