Conformational studies of microcystin-LR using NMR spectroscopy and molecular dynamics calculations

The three-dimensional structures of the cyclic cyanobacterial heptapeptide toxin microcystin-LR was characterized using nuclear magnetic resonance spectroscopy in aqueous and dimethyl sulfoxide (DMSO)/water solutions. Spatial arrangement was further studied by simulated annealing and molecular dynamics calculations. In solution, microcystin-LR predicted a single saddle-shaped backbone conformation with the flat part consisting of the residues Adda5-Glu6-Mdha7. The side segments of Arg4 and the remote portion of Adda5 are described to be pliable with no discernible structures.