Details

Autor(en) / Beteiligte

• Pletnev, V. Z.
• Mikhailova, I. Yu
• Ivanova, V. T.
• Langs, D. A.
• Grochulski, P.
• Duax, W. L.

Titel

The structure of [D-Hyi2, L-Hyi4]meso-valinomycin revealed by X-Ray analysis

Ist Teil von

• Biopolymers, 1991-03, Vol.31 (4), p.409-415

Ort / Verlag

Hoboken: Wiley Subscription Services, Inc., A Wiley Company

Erscheinungsjahr

1991

Quelle

MEDLINE

Beschreibungen/Notizen

• Direct x‐ray analysis has been used to determine the crystal structure of [D‐Hyi2, L‐Hyi4]meso‐valinomycin {cyclo[‐D‐Val‐D‐Hyi‐L‐Val‐L‐Hyi‐(D‐Val‐L‐Hyi‐L‐Val‐D‐Hyi)2‐], C60H102N6O18}, which crystallized from acetone with two solvent molecules. The crystals are trigonal, space group P32, number of molecules per unit cell Z = 3, cell parameters a = b = 15.2085 (8) Å, c = 29.3250 (9) Å, γ = 120°. The standard (R)and weighted (Rw) reliability factors after refinement of the atomic coordinates for C, N, and O atoms in the anisotropic thermal motion approximation, allowing for isotropic H atom contributions, were 0.070 and 0.082, respectively. The molecule adopts a distorted bracelet structure which is stabilized by six NH …︁ OC 4 → 1 type intramolecular hydrogen bonds. The side chains predominantly occupy external pseudoaxial positions relative to the cylindrical axis of the molecule. In contrast to meso‐valinomycin, only four of the six Val carbonyl oxygen atoms are directed inwards to form a coordination centre for the molecule, and the carbonyl oxygen atoms of residues D‐Val1 and L‐Val3 are twisted outward and point away from the centre of the molecule. Although the analogue has a partially formed ion‐binding center, it is inaccessible because the hydrophobic isopropyl groups of the D‐Hyi2 and L‐Hyi4 residues screen the molecular cavity on both sides.