Methyltransferase; part of the gene cluster that mediates the biosynthesis of gramillins A and B, bicyclic lipopeptides that induce cell death in maize leaves but not in wheat leaves (PubMed:30395461). The nonribosomal peptide synthetase GRA1 incorporates respectively a glutamic adic (Glu), a leucine (Leu), a serine (Ser), a hydroxyglutamine (HOGln), a 2-amino decanoic acid, and 2 cysteins (CysB and CysA) (Probable). The biosynthesis of 2-amino decanoic acid incorporated in gramillins could be initiated by a fatty acid synthase composed of the alpha and beta subunits FGSG_00036 and FGSG_11656 (Probable). The cytochrome P450 monooxygenase FGSG_15680 could hydroxylate the fatty acid chain (Probable). Subsequent oxidation to the ketone by the oxidoreductase FGSG_00048 and transamination by aminotransferase FGSG_00049 could form 2-amino-decanoic acid (Probable). On the other hand, FGSG_15680 could also be responsible for the HO-modified glutamine at the gamma-position (Probable). Whether hydroxylation occurs on the fully assembled product or on the Gln residue prior to assembly into the gramillins requires further proof (Probable). The thioredoxin FGSG_00043 could also be required for the disulfide-bond formation between CysA and CysB (Probable). The specific involvement of the remaining proteins from the cluster is more difficult to discern, but could have broader regulatory (FGSG_00040 and FGSG_11657) or enzymatic functions (FGSG_00044 and FGSG_00045) (Probable). The final C-domain of GRA1 does not possess the expected sequence of a termination CT domain, often implicated in macrocyclization and release of a cyclopeptidein fungal NRPs; and the thioesterase FGSG_00047 may act in concert with the terminal C-domain of GRA1 to catalyze the formation of the macrocyclic anhydride and release of the products (Probable). Mycotoxin biosynthesis. Belongs to the class V-like SAM-binding methyltransferase superfamily.