Molecular Cloning, Expression Pattern, and Phylogenetic Analysis of the Lysyl-tRNA Synthetase Gene from the Chinese Oak Silkworm Antheraea pernyi

Abstract

Aminoacyl-tRNA synthetases (AARS) are a class of enzymes that charge tRNAs with their cognate amino acids. There are two classes of tRNA synthetases, classes I and classes II, that are distinguished by the architectures of their active-site catalytic cores (Guo et al., 2008). Lysyl-tRNA synthetase (LysRS) is an AARS, a group of ancient proteins known for their critical role in translation. LysRS is a homodimer localized to the cytoplasm which belongs to the class II family of tRNA synthetases. Its assignment to class II AARS is based upon its structure and the presence of three characteristic sequence motifs in the core domain. The catalytic core domain is primarily responsible for the ATP-dependent formation of the enzyme bound aminoacyl-adenylate. The LysRS gene has been cloned and characterized from various kinds of organisms. In Escherichia coli, there are two distinct LysRSs encoded by two widely separated genes, LysRS and LysRU (VanBogelen et al., 1983; Emmerich & Hirshfield, 1987), while in Campylobacter jejuni only one LysRS is present (Chan & Bingham, 1992). In E. coli, the LysRS gene is expressed constitutively while LysRU can be induced by growth at high temperature (Hirshfield et al., 1981). In human, only one LysRS belonging to the class II family of AARSs is present (Guo et al., 2008). The crystal structure of tetrameric form of human LysRS has been recently determined (Guo et al., 2008). Human LysRS has been shown to be secreted and to trigger a proinflammatory response as a target of autoantibodies in the human autoimmune diseases, polymyositis or dermatomyositis (Park et al., 2005). And, LysRS is required for the translocation of calreticulin to the cell surface in immunogenic death (Kepp et al., 2010). However, none of insect LysRS gene has been characterized to date. The Chinese oak silkworm, Antheraea pernyi (Lepidoptera: Saturniidae), is one of the most well-known economic insect species used for silk production and insect food source. This insect is known to be sucessfully domesticated in China around the 16th century (Liu et al. 2010a), and it is commercially cultivated in China, India, and Korea. To isolate the functional genes of A. pernyi, we have constructed a full-length cDNA library (Li et al. 2009). By EST