Premium
Centrosymmetric bilayers in the 0.75 å resolution structure of a designed alpha‐helical peptide, D, L‐Alpha‐1
Author(s) -
Patterson William R.,
Anderson Daniel H.,
Degrado William F.,
Cascio Duilio,
Eisenberg David
Publication year - 1999
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.8.7.1410
Subject(s) - crystallography , chemistry , peptide , enantiomer , stereochemistry , side chain , crystal structure , alpha helix , helix (gastropod) , molecule , bilayer , circular dichroism , membrane , ecology , biochemistry , organic chemistry , snail , biology , polymer
Abstract We report the 0.75 Å crystal structure of a racemic mixture of the 12‐residue designed peptide “Alpha‐1” (Acetyl‐ELLKKLLEELKG), the L‐enantiomer of which is described in the accompanying paper. Equivalent solutions of the centrosymmetric bilayers were determined by two direct phasing programs in space groups P1 and P1. The unit cell contains two L‐alpha‐helices and two D‐alpha‐helices. The columnar‐sheet bilayer motif seen in L‐Alpha‐1 is maintained in the D, L‐Alpha‐1 structure except that each sheet of head‐to‐tail helices is composed of one enantiomer and is related to its neighboring sheets by inversion symmetry. Comparison to the L‐Alpha‐1 structure provides further insight into peptide design. The high resolution and small asymmetric unit allowed building an intricate model ( R = 13.1%, Rf ree = 14.5%) that incorporates much of the discrete disorder of peptide and solvent. Ethanolamine and 2‐methyl‐2, 4‐pentanediol (MPD) molecules bind near helix termini. Rigid body analysis identifies sites of restricted displacements and torsions. Side‐chain discrete disorder propagates into the backbone of one helix but not the other. Although no side chain in Alpha‐1 is rigid, the environments in the crystal restrict some of them to no or only one active torsion.