Phylogenetic Analysis And Structure Prediction Of KsgA In Cyanobacteria

Cyanobacteria are among the most ancient organisms on the earth, many species of which are important for the ecological environment. However, we know little about the molecular evolution of cyanobacteria. The KsgA/Diml protein family of rRNA adenine dimethyltransferase catalyzes the post-transcriptional dimethylations of two neighboring adenines in the 3'terminal helix of the small ribosomal subunit rRNA. These modifications are conserved throughout evolution of all three kingdoms bacteria, achaea, and eukaryotes. Our research pays attention to molecular evolution and structure of KsgA/Diml family in cyanobacteria. The phylogenetic analysis of 16S rDNA and ksgA gene showed an evolutionary conservation of KsgA/Diml family in cyanobacteria. The homology model of KsgA protein indicated that the fold of KsgA of cyanobacteria is two-domain architecture and the N-terminal methyltransferase core domain is relatively well conserved. Both the putative catalytic center and SAM-binding pocket were analyzed and the functional complementation assay was used to express KsgA from three cyanobacteria Synechocystis sp.PCC6803?Synechococcus elongates PCC7942 and Anabaena sp.PCC7120 in Escherichia coli mutant to detect dimethyltransferase activity. The results indicated that the functions of E.coli ksgA mutanats could be complemented by cyanobacterial ksgA to some extent...