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Crystal structure of Boc‐Leu‐Aib‐Pro‐Val‐Aib‐Aib‐Glu(OBzl)‐Gln‐Phl × H 2 O, the C‐terminal nonapeptide of the voltage‐dependent ionophore alamethicin
Author(s) -
Bosch R.,
Jung G.,
Schmitt H.,
Winter W.
Publication year - 1985
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360240606
Subject(s) - alamethicin , chemistry , antiparallel (mathematics) , hydrogen bond , crystallography , orthorhombic crystal system , stereochemistry , molecule , crystal structure , membrane , bilayer , organic chemistry , biochemistry , physics , quantum mechanics , magnetic field
Boc‐ L ‐Leu‐Aib‐Pro‐Val‐Aib‐Aib‐Glu(OBzl)‐Gln‐Phl (Boc = t ‐butyloxycarbonyl, Aib = α‐aminoisobutyric acid, Bzl = benzyl, Phl = phenylalaninol), C 59 H 90 N 10 O 14 , the protected C‐terminal nonapeptide with the sequence 12–20 of alamethicin, crystallizes in the orthorhombic space group P 2 1 2 1 2 1 with a = 15.666, b = 16.192, c = 26.876 Å, and Z = 4. The molecular conformation is right‐handed helical with three α‐(5 → 1 hydrogen bonds) and three β‐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 α/3 10 r ‐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.