Archaeal Proteins|Binding Sites|Computational Biology|Crystallography, X-Ray|Escherichia coli Proteins|Evolution, Molecular|Guanine|Methanococcus|Methyltransferases|Models, Molecular|Molecular Structure|Predictive Value of Tests|Protein Folding|Protein Structure, Tertiary|Sequence Alignment|Sequence Homology, Nucleic Acid|tRNA Methyltransferases