Sequence Activity Relaqtionships in a Radical Sam Peptide Maturase

Ribosomally synthesized and post-translationally modified peptide Tte1186a and several point mutation variants are synthesized using solid phase peptide synthesis with FMOC amino acids. Substrate recognition and thioether linkage formation from the radical S-adenosyl methionine Tte1186 maturase is determined by analyzing assays with liquid chromatography/mass spectroscopy. Results indicate a very high tolerance to mutation throughout the peptide, allowing of 38 of 41 tested mutations throughout the peptide with only mutations on the crosslinking site and some Cys residues not tolerated. Results did not elucidate a clear pattern of recognition due to the high tolerance observed. Notably, some of the C-terminus Cys residues were important for successful crosslink formations, indicating the possibility of a different mechanism of recognition from other thiopeptide forming radical S-adenosylmethionine enzymes.