Protein crystals can be incommensurately modulated

For a normal periodic crystal, the X‐ray diffraction pattern can be described by an orientation matrix and a set of three integers that indicate the reciprocal lattice points. Those integers determine the spacing along the reciprocal lattice directions. In aperiodic crystals, the diffraction pattern...

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Bibliographic Details
Published in:Journal of applied crystallography 2008-06, Vol.41 (3), p.600-605
Main Authors: Lovelace, Jeffrey J., Murphy, Cameron R., Daniels, Lee, Narayan, Kartik, Schutt, Clarence E., Lindberg, Uno, Svensson, Christer, Borgstahl, Gloria E. O.
Format: Article
Language:English
Subjects:
actin
actin-based motility
angstrom resolution
beta-actin
Biologi
Biology
cell biology
cross-linked profilin
Crystal lattices
Crystal structure
Crystallography
dynamics
f-actin
Fysik
incommensurate crystallography
Medicin och hälsovetenskap
modulated diffraction
modulated protein crystals
muscle
NATURAL SCIENCES
NATURVETENSKAP
Physical Sciences
profilin
Proteins
satellite reflections
Software
state
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Summary:For a normal periodic crystal, the X‐ray diffraction pattern can be described by an orientation matrix and a set of three integers that indicate the reciprocal lattice points. Those integers determine the spacing along the reciprocal lattice directions. In aperiodic crystals, the diffraction pattern is modulated and the standard periodic main reflections are surrounded by satellite reflections. The successful indexing and refinement of the main unit cell and q vector using TWINSOLVE, developed by Svensson [(2003). Lund University, Sweden], are reported here for an incommensurately modulated, aperiodic crystal of a profilin:actin complex. The indexing showed that the modulation is along the b direction in the crystal, which corresponds to an `actin ribbon' formed by the crystal lattice. Interestingly, the transition to the aperiodic state was shown to be reversible and the diffraction pattern returned to the periodic state during data collection. It is likely that the protein underwent a conformational change that affected the neighbouring profilin:actin molecules in such a way as to produce the observed modulation in the diffraction pattern. Future work will aim to trap the incommensurately modulated crystal state, for example using cryocooling or chemical crosslinking, thus allowing complete X‐ray data to be collected.
ISSN:1600-5767
0021-8898
1600-5767
DOI:10.1107/S0021889808010716