Conformational Preferene of Cycloleonuripeptides A, B, and C, Three Proline-Rich Cyclic Nonapeptides from Leonurus heterophyllus

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Three-dimensional structures in dimethyl sulfoxide (DMSO)-d_6 of three proline-rich cyclic nonapeptides, cycloleonuripeptides A : cyclo (-Gly-Pro-Pro-Pro-Tyr-Pro-Pro-Met-Ile-), B : cyclo (-Gly-Pro-Pro-Pro-Tyr-Pro-Pro-Met(O)-Ile-), and C : cyclo (-Gly-Pro-Pro-Pro-Tyr-Pro-Pro-Met(O)-Ile-), which have been isolated from the fruits of Leonurus heterophyllus, were determined by distance geometry calculation and restrained energy minimization from NMR data. Calculation using 272 different initial structures led to a uniquely determined backbone conformation with a root mean square deviation value of 0.57 Å. The backbone structures of cycloleonuripeptides A, B, and C consist of two β-turns, a β VI turn at Pro^3-Pro^4,and a β I turn at Pro^7-Met^8. In addition to a transannular 4→1 backbone hydrogen bond between Tyr^5-NH and Pro^2-CO, two intramolecular hydrogen bonds between Gly^1-NH and Pro^6-CO, and between Ile^9-NH and Pro^6-CO, which constructed a β-bulge conformation, were observed.
社団法人日本薬学会の論文
1997-01-15