Abstract
A thioredoxin-like protein (txl) gene was cloned from the bumblebee, Bombus ignitus. The B. ignitus txl (Bitxl) gene spans 1777 bp and consists of three introns and four exons coding for 285 amino acid residues with a conserved active site (CGPC). The deduced amino acid sequence of the Bitxl cDNA was 65% similar to the Drosophila melanogaster txl. Northern blot analysis revealed the presence of Bitxl transcripts in all tissues examined. When H2O2 was injected into the body cavity of B. ignitus workers, Bitxl mRNA expression was up-regulated in the fat body tissue. In addition, the expression levels of Bitxl mRNA in the fat body greatly increased when B. ignitus workers were exposed to low (4°C) or high (37°C) temperatures, or injected with lipopolysaccharide (LPS), which suggests that the Bitxl possibly protects against oxidative stress caused by extreme temperatures and bacterial infection.
Highlights
Thioredoxins (Trx) are small thiol proteins with a molecular mass of about 12 kDa that are evolutionarily conserved from prokaryotes to higher eukaryotes (Laurent et al, 1964; Holmgren, 1985, 1989)
This paper describes the gene structure and characterization of the txl gene from the bumblebee, Bombus ignitus, which is an important pollinator of various greenhouse crops
The B. ignitus txl (Bitxl) gene consisted of three introns and four exons coding for 285 amino acid residues
Summary
Thioredoxins (Trx) are small thiol proteins with a molecular mass of about 12 kDa that are evolutionarily conserved from prokaryotes to higher eukaryotes (Laurent et al, 1964; Holmgren, 1985, 1989). Trx contains two cysteine residues within the conserved active site sequence (CGPC) and many Trx-like proteins are members of the Trx superfamily (Nakamura, 2005). Trx is a mitochondrial protein with an active site, CGPC that acts as an electron donor for mitochondrial Trx-dependent peroxidase (Spyrou et al, 1997; Araki et al, 1999). The active site sequences of Trx and TRP32 are identical to that of Trx. In addition, some other proteins contain a Trx domain, in which some residues within the active site are changed. Thioredoxinrelated transmembrane protein, TMX, possesses one Trxlike domain with a unique potentially active site sequence, CPAC, and bacterially expressed TMX shows Trx-like reducing activity in vitro (Matsuo et al, 2001). The Trx-like domain is present in a nuclear protein termed nucleoredoxin with a modified active site sequence, CPPC (Kurooka et al, 1997)
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