The structure of form II crystals of bovine pancreatic trypsin inhibitor has been investigated by joint refinement of X-ray and neutron data. Crystallographic R factors for the final model were 0.200 for the X-ray data extending to 1 A resolution and 0.197 for the 1 ...
The structure of form II crystals of bovine pancreatic trypsin inhibitor has been investigated by joint refinement of X-ray and neutron data. Crystallographic R factors for the final model were 0.200 for the X-ray data extending to 1 A resolution and 0.197 for the 1.8 A neutron data. This model was strongly restrained, with 0.020 A root-mean-square (r.m.s.) departure of bond lengths from their ideal values and 0.019 A r.m.s. departure of planar groups from planarity. The resulting structure was very similar to that of crystal form I (r.m.s. deviation for main chain atoms was 0.40 A); nevertheless larger deviations were observed in particular regions of the chain. Twenty out of 63 ordered water molecules occupy similar positions (deviation less than 1 A) in both models. Eleven amide hydrogens were found to be protected from exchange after three months of soaking the crystals in deuterated mother liquor at pH 8.2. Their locations were in excellent agreement with the results obtained by two-dimensional nuclear magnetic resonance, but the rates of exchange are much lower in the crystalline state.
Related Citations:
Comparison of Two Highly Refined Structures of Bovine Pancreatic Trypsin Inhibitor Wlodawer, A., Deisenhofer, J., Huber, R. (1987) J Mol Biol 193: 145
Pancreatic Trypsin Inhibitor. A New Crystal Form and its Analysis Walter, J., Huber, R. (1983) J Mol Biol 167: 911
Organizational Affiliation:
A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninski pr. 59, Moscow, 117333, Russia.
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