Interactions between the methylation sites of the Escherichia coli aspartate receptor mediated by the methyltransferase.

Mutations made at and near the methylation sites of the Escherichia coli aspartate receptor were found to affect the methylation rates of the remaining methylation sites. The results supported a model in which the methyltransferase enzyme contacts a residue seven amino acids to the C terminus of a site being methylated. The presence of a negatively charged residue at that position inhibits methylation, whereas a neutral residue has no effect. Methylation sites in the wild type receptor may also influence the methylation of other sites which are 7 residues away through a physical contact with the methyltransferase.