Volume 15, No 6, Jun 2005
ISSN: 1001-0602
EISSN: 1748-7838 2018
impact factor 17.848*
(Clarivate Analytics, 2019)
Volume 15 Issue 6, June 2005: 474-482
ORIGINAL ARTICLES
Identification, characteristic and phylogenetic analysis of type II DNA topoisomerase gene in Giardia lamblia
De He1, 2, 3, Jian Fan Wen1,*, Wan Qun Chen1, Si Qi Lu4, De Dong Xin1, 2
1 Key Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
2 Gradulate School of the Chinese Academy of Sciences, Beijing 100039, China
3 Southwest Forestry College, Kunming 650224, China
4Capital University of Medical Sciences, Beijing 100054, China
Correspondence: Jian Fan WEN(wenjf@mail.kiz.ac.cn)
The genes encoding type II DNA topoisomerases were investigated in Giardia lamblia genome, and a type IIA gene, GlTop 2 was identified. It is a single copy gene with a 4476 bp long ORF without intron. The deduced amino acid sequence shows strong homology to eukaryotic DNA Top 2. However, some distortions were found, such as six insertions in the ATPase domain and the central domain, a ~100 aa longer central domain; a ~200 aa shorter C-terminal domain containing rich charged residues. These features revealed by comparing with Top 2 of the host, human, might be helpful in exploiting drug selectivity for antigiardial therapy. Phylogenetic analysis of eukaryotic enzymes showed that kinetoplastids, plants, fungi, and animals were monophyletic groups, and the animal and fungi lineages shared a more recent common ancestor than either did with the plant lineage; microsporidia grouped with fungi. However, unlike many previous phylogenetic analyses, the "amitochondriate" G. lamblia was not the earliest branch but diverged after mitochondriate kinetoplastids in our trees. Both the finding of typical eukaryotic type IIA topoisomerase and the phylogenetic analysis suggest G. lamblia is not possibly as primitive as was regarded before and might diverge after the acquisition of mitochondria. This is consistent with the recent discovery of mitochondrial remnant organelles in G. lamblia.
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