Characterization of a silkworm thioredoxin peroxidase that is induced by external temperature stimulus and viral infection.
A thioredoxin peroxidase (TPx) that reduces H(2)O(2) was firstly characterized in the lepidopteran insect, silkworm Bombyx mori. The B. mori TPx (BmTPx) cDNA contains an open reading frame of 585 bp encoding 195 amino acid residues and possesses two cysteine residues that are characteristic of 2-Cys subgroup of peroxiredoxin family. The deduced amino acid sequence of the BmTPx cDNA showed 78% identity to Drosophila melanogaster (DmTPx-1), 73% to Aedes aegypti (AaTPx), and 54-48% to other insect 2-Cys TPx. The cDNA encoding BmTPx was expressed as a 25-kDa polypeptide in baculovirus-infected insect Sf9 cells. The purified recombinant BmTPx was shown to reduce H(2)O(2) in the presence of electrons donated by dithiothreitol and shown to be active in the presence of thioredoxin as electron donor. Northern blot analysis revealed the presence of BmTPx transcripts in all tissues examined. Western blot analysis showed the presence of the BmTPx in the fat body and midgut, but not in the hemolymph, suggesting the BmTPx is not secretable. When H(2)O(2) was injected into body cavity of B. mori larva, BmTPx mRNA expression was up-regulated in the fat body tissues. Interestingly, the expression levels of BmTPx enzyme in the fat body were particularly high when B. mori larva was exposed at low (4 degrees C) and high (37 degrees C) temperatures or baculovirus infection, suggesting that the BmTPx seems to play a protective role against oxidative stress caused by temperature stimuli and viral infection.
Lee
Kwang Sik
KS
College of Natural Resources and Life Science, Dong-A University, Busan 604-714, Republic of Korea.
Kim
Seong Ryul
SR
Park
Nam Sook
NS
Kim
Iksoo
I
Kang
Pil Dong
PD
Sohn
Bong Hee
BH
Choi
Kwang Ho
KH
Kang
Seok Woo
SW
Je
Yeon Ho
YH
Lee
Sang Mong
SM
Sohn
Hung Dae
HD
Jin
Byung Rae
BR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000201:enzymology* / Q000235:genetics / Q000821:virology*; D002460:Cell Line; D004790:Enzyme Induction; D007814:Larva / Q000201:enzymology; D008969:Molecular Sequence Data; D017924:Nucleopolyhedroviruses; D010544:Peroxidases / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics; D054464:Peroxiredoxins; D011994:Recombinant Proteins / Q000096:biosynthesis; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013696:Temperature
D011994:Recombinant Proteins; D010544:Peroxidases; D054464:Peroxiredoxins