Crystalline Aggregates of the Repetitive Polypeptide {(AlaGly)3GluGly(GlyAla)3GluGly}10: Structure and Dynamics Probed by 13C Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy
Received August 31, 1995 Revised Manuscript Received November 17, 1995 Abstract: A repetitive polymer comprising 10 repeats of the oligopeptide
(AlaGly)3GluGly(GlyAla)3
GluGly has been synthesized via bacterial expression of an artificial
gene. This polymer was designed
to assemble into lamellar crystals of predictable thickness, with the
oligo(AlaGly) and oligo(GlyAla) portions
forming the crystal stems and the polar, bulky Glu residues lying in
reverse turns between adjacent,
antiparallel Download the full text:
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and
-strands. The solid-state structure and dynamics
of this material, before and after
crystallization, have been probed with a range of magic angle spinning
13C NMR experiments. Chemical
shifts of backbone carbons indicate that the oligo(AlaGly)
elements adopt -conformations in all samples.
Changes in both the chemical shift and cross-polarization behavior
of the alanine side chains upon
crystallization provide evidence for location of alanine within the
crystalline -sheet regions. In contrast,
although crystallization induces changes in the chemical shift of
C
of the glutamic acid residue, no change
occurs in the dynamic behavior of the Glu side chain carbons. The
latter observation suggests that this
side chain is excluded from the crystalline region and supports the
assignment of Glu to turn positions
at the lamellar surface.
