title: NMR structure of Carcinoscorpius rotundicauda thioredoxin-related protein 16 and its role in regulating transcription factor NF-κB activity.
abstract: Thioredoxins (Trxs), which play a key role in maintaining a redox environment in the cell, are found in almost all organisms. Trxs act as potential reducing agents of disulfide bonds and contain two vicinal cysteines in a CXXC motif at the active site. Trx is also known to activate the DNA binding activity of NF-κB, an important transcription factor. Previously, Trx-related protein 16 from Carcinoscorpius rotundicauda (Cr-TRP16), a 16-kDa Trx-like protein that contains a WCPPC motif, was reported. Here we present the NMR structure of the reduced form of Cr-TRP16, along with its regulation of NF-κB activity. Unlike other 16-kDa Trx-like proteins, Cr-TRP16 contains an additional Cys residue (Cys-15, at the N terminus), through which it forms a homodimer. Moreover, we have explored the molecular basis of Cr-TRP16-mediated activation of NF-κB and showed that Cr-TRP16 exists as a dimer under physiological conditions, and only the dimeric form binds to NF-κB and enhances its DNA binding activity by directly reducing the cysteines in the DNA-binding motif of NF-κB. The C15S mutant of Cr-TRP16 was unable to dimerize and hence does not bind to NF-κB. Based on our finding and combined with the literature, we propose a model of how Cr-TRP16 is likely to bind to NF-κB. These findings elucidate the molecular mechanism by which NF-κB activation is regulated through Cr-TRP16.
authors: Department of Biological Sciences, National University of Singapore, Singapore 117543.
authors: Pankaj Kumar
authors: PK
authors: Giri
authors: Fan
authors: F
authors: Jing-Song
authors: Muthu K
authors: MK
authors: Shanmugam
authors: Jeak Ling
authors: JL
authors: Ding
authors: Gautam
authors: G
authors: Sethi
authors: Kunchithapadam
authors: K
authors: Swaminathan
authors: J
authors: J
authors: Sivaraman
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D060829:Arthropod Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006737:Horseshoe Crabs / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D016328:NF-kappa B / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013879:Thioredoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D060829:Arthropod Proteins; D016328:NF-kappa B; D013879:Thioredoxins