Conformational and functional similarities between glutaredoxin and thioredoxins.

Abstract

The tertiary structures of thioredoxin from Escherichia coli and bacteriophage T4 have been compared and aligned giving a common fold of 68 C alpha atoms with a root mean square difference of 2.6 A. The amino acid sequence of glutaredoxin has been aligned to those of the thioredoxins assuming that glutaredoxin has the same common fold. A model of the glutaredoxin molecule was built on a vector display using this alignment and the T4 thioredoxin tertiary structure. By comparison of the model with those of the thioredoxins, we have identified a molecular surface area on one side of the redox‐active S‐S bridge which we suggest is the binding area of these molecules for redox interactions with other proteins. This area comprises residues 33‐34, 75‐76 and 91‐93 in E. coli thioredoxin; 15‐16, 65‐66 and 76‐78 in T4 thioredoxin and 12‐13, 59‐60 and 69‐71 in glutaredoxin. In all three molecules, this part of the surface is flat and hydrophobic. Charged groups are completely absent. In contrast, there is a cluster of charged groups on the other side of the S‐S bridge which we suggest participates in the mechanisms of the redox reactions. In particular, a lysine residue close to an aromatic ring is conserved in all molecules.

Further characterization and amino acid sequence of m-type thioredoxins from spinach chloroplasts

“…1) and that thioredoxin m can replace thioredoxin from E. coli in the complementation of an active DNA polymerase as we have reported earlier [17]. More recent conformational studies on E. coli thioredoxin [45] have shown that Gly-33, Pro-34, Ile-75, Pro-76, Val-91, Gly-92 and Ala-93 make up a hydrophobic region on the protein surface and that this hydrophobic area may be responsible for the redox interactions of thioredoxins with other proteins. Most of these residues are conserved in thioredoxin m (see Fig.…”

Purification, characterization and revised amino acid sequence of a second thioredoxin from Corynebacterium nephridii

“…Additional significant changes in the chemical shifts of the backbone protons were observed for residues 58, 60-62, 73-77 and 92. The X-ray structure of oxidized thioredoxin shows that many of the residues that undergo these significant conformational changes upon reduction form a flat hydrophobic surface, which is probably involved in the interaction with other proteins [43]. Lim et al, using Anabaena 7119/E.…”

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

“…They are highly similar in spite of large differences in amino acid sequence. Models were built for C. nephridii [6] and Anabaena [17] which showed that these two proteins can also adopt similar folding.In the present study we have determined the amino acid sequence of thioredoxin from Rb. sphaeroides Y, and proposed a three-dimensional model derived from the E. coEi crystallographic structure, as a first step toward the understanding of an important aspect of the regulation of bacteriochlorophyll synthesis in Rb.…”

“…They are highly similar in spite of large differences in amino acid sequence. Models were built for C. nephridii [6] and Anabaena [17] which showed that these two proteins can also adopt similar folding.…”

“…These last two functions have an absolute requirement for thioredoxin as shown by genetic techniques; however, the active-site redox activity is not essential, whereas the reduced conformation of thioredoxin plays so far unknown roles. 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.…”