Conserved domain analysis
We obtained information of conserved domains using the NCBI online Conserved Domain-search tool (http://www.ncbi.nlm.nih.gov/Structure/cdd/wrpsb.cgi) and Conserved Domain Database (CDD) (http://www.ncbi.nlm.nih.gov/Structure/cdd/cdd.shtml) [22, 23]. After the matching CDD model and the corresponding Conserved Domain Tree (CDTree) were identified, the CysQ sequence was added to the matched model, and the corresponding CDTree was then recalculated.