Mechanistic Insights into Roseoflavin Synthesis by N,N-8-Demethyl-8-aminoriboflavin Dimethyltransferase (RosA): Molecular Dynamics Simulations and Residue Conservation Analysis

Abstract

8-Demethyl-8-dimethylaminoriboflavin (Roseoflavin or RoF) is a natural riboflavin analogue found in Streptomyces davaonensis and Streptomyces cinnabarinus. RoF displays potent antibiotic properties because it affects FMN riboswitches and flavoproteins of cellular targets. N,N-8-Demethyl-8-aminoriboflavin dimethyltransferase (RosA) is an enzyme that catalyzes the last step of RoF biosynthesis, a consecutive dimethylation of 8-demethyl-8-aminoriboflavin (AF) to generate RoF. Thus, understanding mechanistic insights into RosA structures and mechanisms could lead to the improvement of the RoF product yield. Herein, mechanistic insights into roseoflavin synthesis by RosA were evaluated using molecular dynamics simulations. The obtained results revealed that RosA possibly catalyzes the reaction by positioning the substrate binding to have proper distance and orientation to the methyl group donor, S-adenosylmethionine. No direct participation of catalytic residues in the reaction was identified. The enzyme’s active site structures change drastically to accommodate the ligand binding. On the basis of the MM/GBSA calculations and conservation analysis, the amino acid residues involved in substrate binding were identified. The structural information obtained from this study could be beneficial in designing RosA to efficiently produce roseoflavin.