alpha-N-Methyltransferase regiospecificity is mediated by proximal, redundant enzyme-substrate interactions.
Crone, K.K., Labonte, J.W., Elias, M.H., Freeman, M.F.(2025) Protein Sci 34: e70021-e70021
- PubMed: 39840790
- DOI: https://doi.org/10.1002/pro.70021
- Primary Citation of Related Structures:
9CGW, 9CH0, 9CH1, 9CH2, 9CH3, 9CH5, 9CH7, 9CHI, 9CHK - PubMed Abstract:
N-Methylation of the peptide backbone confers pharmacologically beneficial characteristics to peptides that include greater membrane permeability and resistance to proteolytic degradation. The borosin family of ribosomally synthesized and post-translationally modified peptides offer a post-translational route to install amide backbone α-N-methylations. Previous work has elucidated the substrate scope and engineering potential of two examples of type I borosins, which feature autocatalytic precursors that encode N-methyltransferases that methylate their own C-termini in trans. We recently reported the first discrete N-methyltransferase and precursor peptide from Shewanella oneidensis MR-1, a minimally iterative, type IV borosin that allowed the first detailed kinetic analyses of borosin N-methyltransferases. Herein, we characterize the substrate scope and resilient regiospecificity of this discrete N-methyltransferase by comparison of relative rates and methylation patterns of over 40 precursor peptide variants along with structure analyses of nine enzyme-substrate complexes. Sequences critical to methylation are identified and demonstrated in assaying minimal peptide substrates and non-native peptide sequences for assessment of secondary structure requirements and engineering potential. This work grants understanding towards the mechanism of substrate recognition and iterative activity by discrete borosin N-methyltransferases.
Organizational Affiliation:
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Twin Cities, St. Paul, Minnesota, USA.