title: Thioredoxin from Brugia malayi: defining a 16-kilodalton class of thioredoxins from nematodes.
abstract: Thioredoxins are a family of small redox proteins that undergo NADPH-dependent reduction by thioredoxin reductase. This results in a supply of reducing equivalents that cells use in a wide variety of biological reactions, which include maintaining reduced forms of the enzymes important for protection against damage from high-energy oxygen radicals, the regulation of transcription factor activity, and the inhibition of apoptosis. Here we report on a new member of the thioredoxin family of proteins from the filarial nematode Brugia malayi, Bm-TRX-1, which defines a new subclass of 16-kDa thioredoxins that occur widely in nematodes, including Caenorhabditis elegans. In addition to being larger than the thioredoxins found in mammalian and bacterial species, the putative active site sequence of Bm-TRX-1, WCPPC, does not conform to the highly conserved WCGPC reported for thioredoxins from mammals to bacteria. Interestingly, an allelic form of Bm-TRX-1 was identified with an active site sequence WCPQC, which appears to be unique to the thioredoxins from filarial species. Bm-TRX-1 was between 98% and 35% identical to thioredoxins from other nematodes and approximately 20% identical to the thioredoxins from mammals and Escherichia coli. Bm-TRX-1 was constitutively transcribed throughout the B. malayi life cycle, and Bm-TRX protein was detectable in somatic extracts and excretory-secretory products from adults and microfilariae. Recombinant Bm-TRX-1 had thiodisulfide reductase activity, as measured by the reduction of insulin, and protected DNA from the nicking activity of oxygen radicals. Overexpression of Bm-TRX-1 in a human monocyte cell line negatively regulated tumor necrosis factor alpha-induced p38 mitogen-activated protein kinase activity, suggesting a possible role of the 16-kDa Bm-TRX-1 in immunomodulation.
authors.affiliation: Centre for Biotechnology, Anna University, Chennai, India.
authors.forename: Kannan
authors.initials: K
authors.lastname: Kunchithapautham
authors.forename: B
authors.initials: B
authors.lastname: Padmavathi
authors.forename: R B
authors.initials: RB
authors.lastname: Narayanan
authors.forename: P
authors.initials: P
authors.lastname: Kaliraj
authors.forename: Alan L
authors.initials: AL
authors.lastname: Scott
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017178:Brugia malayi / Q000737:chemistry*; D002384:Catalysis; D003001:Cloning, Molecular; D004789:Enzyme Activation; D015801:Helminth Proteins / Q000235:genetics* / Q000502:physiology; D007328:Insulin / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D013879:Thioredoxins / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D000975:Antioxidants; D015801:Helminth Proteins; D007328:Insulin; D013879:Thioredoxins; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases