Bassianolide nonribosomal synthetase that mediates the biosynthesis of bassianolide (BSL), a non-ribosomal cyclodepsipeptide that shows insecticidal and cancer cell antiproliferative activity (PubMed:19285149, PubMed:23608474, PubMed:23727842, PubMed:29163920, PubMed:31471217, PubMed:31388353). BSLS first catalyzes the iterative synthesis of an enzyme-bound dipeptidol monomer intermediate from D-2-hydroxyisovalerate and L-leucine before performing the condensation and cyclization of 4 dipeptidol monomers to yield the cyclic tetrameric ester bassianolide (PubMed:23608474, PubMed:23727842, PubMed:29163920, PubMed:31471217, PubMed:31388353). The N-methyltransferase MT domain is responsible for the methylation of the leucine residues of bassianolide (PubMed:29163920, PubMed:31388353). BSLS is flexible with both the amino acid and hydroxyl acid precursors, and produces bassianolide as the major product (containing N-methyl-L-Leu), together with small amounts of beauvericin and its analogs beauvericins A-C (containing N-methyl-L-Phe) (PubMed:31388353). 4 (R)-2-hydroxy-3-methylbutyrate + 8 ATP + 4 L-leucine + 4 S-adenosyl-L-methionine = 8 AMP + bassianolide + 8 diphosphate + 8 H(+) + 4 S-adenosyl-L-homocysteine Expression is induced during insect infection. NRP synthetases are composed of discrete domains (adenylation (A), thiolation (T) or peptidyl carrier protein (PCP) and condensation (C) domains) which when grouped together are referred to as a single module. Each module is responsible for the recognition (via the A domain) and incorporation of a single amino acid into the growing peptide product. Thus, an NRP synthetase is generally composed of one or more modules and can terminate in a thioesterase domain (TE) that releases the newly synthesized peptide from the enzyme. Occasionally, additional domains required for further modifications are also present (Probable). Bassianolide synthetase has the C1-A1-T1-C2-A2-MT-T2a-T2b-C3 domain organization. During catalysis, C3 and C2 take turns to incorporate the two biosynthetic precursors into the growing depsipeptide chain that swings between T1 and T2a/T2b with C3 cyclizing the chain when it reaches the full length (PubMed:23727842, PubMed:29163920, PubMed:31471217, PubMed:31388353). The N-methyltransferase MT domain in module 2 is responsible for the methylation of the leucine residues integrated in the backbone structure (PubMed:29163920, PubMed:31388353). Abolishes the production of bassianolide but does not affect the biosynthesis of beauvericin (PubMed:19285149). Attenuates the virulence against insects, including the corn earworm (Helicoverpa zea), the fall armyworm (Spodoptera exigua) and the greater wax moth (Galleria mellonella) (PubMed:19285149). Shows insecticidal activity and contributes to the virulence of the fungus against insects including the corn earworm (Helicoverpa zea), the fall armyworm (Spodoptera exigua) and the greater wax moth (Galleria mellonella) (PubMed:19285149). Bassianolide possesses antitumor activities and displays significant cytotoxicity against several human tumor cell lines, including A549, SK-OV-3, HepG2, HCT-15, MCF-7 and MDA-MB 231 cell lines with IC(50) values of 7.24, 8.44, 15.39, 6.40, 11.42 and 3.98 ug/ml respectively (PubMed:27676608). Bassianolide especially induces G0/G1 arrest associated with a decrease of cyclin A, D1 and an increase of p53, MDM2, and p21 expression in human breast adenocarcinoma cell lines (PubMed:27676608). Belongs to the NRP synthetase family.