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X-ray crystal structures of a severely desiccated protein

Published online by Cambridge University Press:  01 October 1999

JEFFREY A. BELL
Affiliation:
Division of Molecular Medicine, Wadsworth Center, New York State Department of Health, P.O. Box 509, Empire State Plaza, Albany, New York 12201-0509
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Abstract

Unlike most protein crystals, form IX of bovine pancreatic ribonuclease A diffracts well when severely dehydrated. Crystal structures have been solved after 2.5 and 4 days of desiccation with CaSO4, at 1.9 and 2.0 Å resolution, respectively. The two desiccated structures are very similar. An RMS displacement of 1.6 Å is observed for main-chain atoms in each structure when compared to the hydrated crystal structure with some large rearrangements observed in loop regions. The structural changes are the result of intermolecular contacts formed by strong electrostatic interactions in the absence of a high dielectric medium. The electron density is very diffuse for some surface loops, consistent with a very disordered structure. This disorder is related to the conformational changes. These results help explain conformational changes during the lyophilization of protein and the associated phenomena of denaturation and molecular memory.

Type
Research Article
Copyright
© 1999 The Protein Society

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