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NrdH‐redoxin of Corynebacterium ammoniagenes forms a domain‐swapped dimer
Author(s) -
Stehr Matthias,
Lindqvist Ylva
Publication year - 2004
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.20126
Subject(s) - thioredoxin , dimer , thioredoxin reductase , stereochemistry , chemistry , monomer , glutaredoxin , ferredoxin thioredoxin reductase , structural motif , hydrogen bond , biochemistry , crystallography , enzyme , molecule , organic chemistry , polymer
NrdH‐redoxins constitute a family of small redox proteins, which contain a conserved CXXC sequence motif, and are characterized by a glutaredoxin‐like amino acid sequence but a thioredoxin‐like activity profile. Here we report the structure of Corynebacterium ammoniagenes NrdH at 2.7 Å resolution, determined by molecular replacement using E. coli NrdH as model. The structure is the first example of a domain‐swapped dimer from the thioredoxin family. The domain‐swapped structure is formed by an inter‐chain two‐stranded anti‐parallel β‐sheet and is stabilized by electrostatic interactions at the dimer interface. Size exclusion chromatography, and MALDI‐ESI experiments revealed however, that the protein exists as a monomer in solution. Similar to E. coli NrdH‐redoxin and thioredoxin, C. ammoniagenes NrdH‐redoxin has a wide hydrophobic pocket at the surface that could be involved in binding to thioredoxin reductase. However, the loop between α2 and β3, which is complementary to a crevice in the reductase in the thioredoxin–thioredoxin reductase complex, is the hinge for formation of the swapped dimer in C. ammoniagenes NrdH‐redoxin. C. ammoniagenes NrdH‐redoxin has the highly conserved sequence motif W61‐S‐G‐F‐R‐P‐[DE]67 which is unique to the NrdH‐redoxins and which determines the orientation of helix α3. An extended hydrogen‐bond network, similar to that in E. coli NrdH‐redoxin, determines the conformation of the loop formed by the conserved motif. Proteins 2004. © 2004 Wiley‐Liss, Inc.