Crystal structure of Boc-Leu-Aib-Pro-Val-Aib-Aib-Glu(OBzl)-Gln-Phl × H2O, the C-terminal nonapeptide of the voltage-dependent ionophore alamethicin
✍ Scribed by R. Bosch; G. Jung; H. Schmitt; W. Winter
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1985
- Tongue
- English
- Weight
- 929 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Boc-L-Leu-Aib-Pro-Val-AibAibGlu(OBz1)-Gln-Phl (Boc = t-butyloxycarbonyl, Aib = a-aminoisobutyric acid, Bzl = benzyl, Phl = phenylalaninol), C59H,Nlo0,,, the protected C-terminal nonapeptide with the sequence 12-20 of alamethicin, crystallize: in the orthorhombic space group P2,2121 with a = 15.666, b = 16.192, c = 26.876 A, and 2 1 4. The molecular conformation is right-handed helical with three a45 + 1 hydrogen bonds) and three p-turns (4 -1 hydrogen bonds). All but two of the hydrogen bonds are significantly longer than the usual value and show bifurcation to some extent. The a/3io-helical nonapeptide molecules are arranged head-to-tail along the a direction. The resulting linear antiparallel chains are linked by a weak intermolecular hydrogen bridge, thus forming a two-dimensional layer structure in the ab plane. The conformation of this nonapeptide is almost identical with that of the corresponding C-terminal part found by x-ray crystallography of the eicosapeptide alamethicin.