Three-dimensional structure of thioredoxin induced by bacteriophage T4.

Abstract

The three-dimensional structure of thioredoxin from bacteriophage T4 has been determined from a 2.8-A resolution electron density map. Phase angles for this map were determined from one heavy atom derivative and anomalous differences from cadmium in the native crystals. The molecule of 87 amino acid residues is built up from two sim le folding units; a " unit from the amino end of the chain anJ a #a unit from the carboxyl end. This structure is similar to that of thioredoxin from Escherichia coli in spite of their completely different amino acid sequences. The redox-active S-S bridge is part of a protrusion of the molecule as in E coli thioredoxin, but with quite different surroundings. The structural differences in this region have been correlated to differences in specificity towards the enzyme ribonucleotide reductase from different species. Thioredoxins are small proteins, containing one redoxactive disulfide bridge, which can function as electron carriers in the synthesis of deoxyribonucleotides from the corresponding ribonucleotides (1). This enzymatic reduction is catalyzed by ribonucleotide reductase. The electrons needed for the reduction are provided by NADPH and transferred via the flavoprotein thioredoxin reductase to the oxidized form of thioredoxin.When Escherichia colh cells are infected by bacteriophage T4, a phage-coded thioredoxin, T4 thioredoxin, is produced. In the phage-infected cells T4 thioredoxin brings about an electron flow from NADPH via the bacterial thioredoxin reductase to a phage-specific ribonucleotide reductase (2).Apart from the thioredoxin system there exists another recently discovered hydrogen donor system for ribonucleotide reductase in E. coli composed of NADPH, glutathione reductase, glutathione, and a small protein called glutaredoxin (3). Glutaredoxin seems to have certain features in common with thioredoxins. It interacts with both E. cob and T4 ribonucleotide reductases, but does not show any interaction with thioredoxin reductase from E. coli (A. Holmgren, personal communication).The molecular properties of thioredoxins from several species,--have been studied (4-8). The amino acid sequence of the 108 residues in thioredoxin from E. coli is known (4) as well as the tertiary structure of the molecule (5).The polypeptide chain of T4 thioredoxin consists of 87 amino acid residues of known sequence (6). No sequence homology can be observed between E. colh and T4 thioredoxin. Crystals of T4 thioredoxin were recently obtained from Cd2+-containing solutions (9). Here we report the three dimensional structure to 2.8-A resolution of these crystals.We initiated this study in order to answer several questions: Is there a similarity between T4 and E. coli thioredoxins in tertiary structure, although no obvious similarity in primary structure is seen? Can the strict specificity of T4 thioredoxin towards the phage-induced ribonucleotide reductase be explained in terms of three-dimensional structure? Is it possible to locate an interaction site with E. coli thioredoxin redu...

Glutaredoxin-3 from Escherichia coli

“…The first crystal structure of a glutaredoxin was that of the phage T4 glutaredoxin (Söderberg et al, 1978). Together, these studies established the now typical thioredoxin/glutaredoxin polypeptide fold (Eklund et al, 1984).…”

Amino acid sequence determination and three‐dimensional modelling of thioredoxin from the photosynthetic bacterium Rhodobacter sphaeroides Y

“…7119 [ll], phage T4 [12] and spinach [13]; the almost complete sequence of thioredoxin from Chromatiurn vinosum has just appeared [14]. Threedimensional structures based on X-ray crystallographic data have been reported for thioredoxin from E. coli [15] and phage T4 [16]. They are highly similar in spite of large differences in amino acid sequence.…”

“…Furthermore, the hydrophobic surface area of thioredoxin, thought to interact with proteins [6], also seems essential for the filamentous phage assembly machinery [7] and the function of the gene-5 protein in the phage T7 DNA polymerase enzyme [S]. It is, therefore, essential to know the threedimensional structures of thioredoxins in order to understand the mechanisms of regulation achieved by this protein.Complete amino acid sequences are presently known for thioredoxin from five organisms: E. coli [9] [16]. They are highly similar in spite of large differences in amino acid sequence.…”

“…Complete amino acid sequences are presently known for thioredoxin from five organisms: E. coli [9] [16]. They are highly similar in spite of large differences in amino acid sequence.…”

Remote Thioredoxin Recognition Using Evolutionary Conservation and Structural Dynamics

“…A cis -proline is also conserved within the active site, though it is distant in sequence to the active cysteines (Eklund et al, 1991; Martin, 1995). With these exceptions, members of the thioredoxin family possess significant sequence diversity, while members of the thioredoxin fold class possess prominent structural similarities (Atkinson and Babbitt, 2009; Eklund et al, 1991; Soderberg et al, 1978). As a result, the thioredoxin protein family presents a challenge for function prediction methods.…”