Figure 1

Structure of the microcystin synthetase ( mcy ) gene and microcystins. Structural representation of microcystin variants and the microcystin synthetase (mcy) gene cluster [5]. General numbering of amino acids is indicated in gray. Arrows indicate the proposed involvement of the product of each mcy marker locus in the incorporation and/or modification of each amino acid into the microcystin. Note that the amino acids (X and Z) and groups (R₁) highlighted in gray are variable. Microcystin is abbreviated as "MCY" in the right-hand table. Abbreviations for three uncommon amino acids in microcystins are as follows: _D-MeAsp, _D-erythro-β-methylaspartic acid; Adda, (2S, 3S, 8S, 9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid; MdhA, N-methyldehydroalanine. The positions of PCR primers in the mcy genes are indicated by a gray box.