2007 Fiscal Year Final Research Report Summary
Study of the mechanism of phase transition of protein crystals and its application to the improvement of diffraction quality of crystals
| Project/Area Number |
18570155
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Biophysics
|
|---|
| Research Institution | National Institute of Advanced Industrial Science and Technology |
|---|
Principal Investigator |
HARATA Kazuaki National Institute of Advanced Industrial Science and Technology, Biological Information Research Center, Principal Research Investigator (20357817)
|
|---|
| Project Period (FY) |
2006 – 2007
|
| Keywords | Biological macromolecule / Protein / X-ray analysis |
|---|
| Research Abstract |
The aim of this research theme is to elucidate the mechanism of the phase transition of protein crystals by means of X-ray diffraction, crystal structure analysis at atomic resolution before and after the transition, and the analysis of thermal motion in the crystalline state.
To obtain atomic resolution crystals of hen egg-white lysozyme, the crystallization was performed by using D_2O instead of H_2O, and two types of monoclinic crystals were obtained. Furthermore, the type II crystal was prepared at some different. NaCl concentrations to investigate the effect of sodium ion. The phase transition induced by dehydration was observed for the two types of crystals, and the change of the X-ray diffraction image indicated that the transition proceeded via intermediate state. The type II crystal took more time for the crystal transformation than the type I crystal, and much more time was required for the transformation of type II crystal prepared m high sodium concentration.
The crystal stru
… More
cture was determined at atomic resolution for crystals before and after the phase transition. In the type I crystal, a sodium ion bound to the sodium binding site was released in the phase transition, while a sodium ion was still bound in the transformed native type II crystal. However, in the transformed type II crystal that was soaked in a saturated NaCl solution, the sodium ion was not observed at the sodium binding site, instead, a sodium ion was bound at the active center. This indicates that the sodium ion controls the structural change in the crystal transformation induced by dehydration.
A new method to analyze the thermal motion of proteins based on the isotropic thermal parameters was developed to investigate the dynamic motion of proteins before and after the phase transition. The method based on the pseudo-anisotropic thermal factors was tested for more than 200 crystal structures, and statistically good agreement was achieved in the comparison with the result from the analysis of observed anisotropic thermal parameters. The application of the method to the structures before and after the phase transition made it possible to compare the dynamic state of the protein structure, and indicated the importance of suppressing the rigid-body motion for the improvement of the diffraction quality of protein crystals. Less
|
