Homology modelling of the DNA 5mC methyltransferase M.BssHII. Is permutation of functional subdomains common to all subfamilies of DNA methyltransferases

Abstract This work presents a full tertiary model of the M. Bss HII methyltransferase (MTase) complexed with substrate DNA and cofactor S -adenosyl- l -methionine, built by homology modelling based on previously solved complete structures of DNA MTases M. Hae III and M. Hha I. M. Bss HII and the template proteins show high sequence similarity, which indicates that they are evolutionary related. However, they are topologically different: M. Bss HII is a circularly permuted variant of template MTases (Xu et al. Nucleic Acids Res 1997;25:3991). The model developed in this work will be a good starting point and valuable help in designing mutagenesis experiments to better understand the biological function of methyltransferases and the process of domain swapping.