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Solution structure calculations through self-orientation in a magnetic field of a cerium(III) substituted calcium-binding protein
被引:40
作者:
Bertini, I
Janik, MBL
Liu, GH
Luchinat, C
Rosato, A
机构:
[1] Univ Florence, Dept Chem, I-50121 Florence, Italy
[2] Univ Florence, Ctr Risonanze Magnet, I-50019 Sesto Fiorentino, Italy
[3] Dept Agr Biotechnol, I-50100 Florence, Italy
关键词:
partial orientation;
paramagnetism;
magnetic susceptibility;
lanthanides;
solution structure;
D O I:
10.1006/jmre.2000.2218
中图分类号:
Q5 [生物化学];
学科分类号:
071010 ;
081704 ;
摘要:
Within the frame of a research aimed at characterizing paramagnetic metal ions capable of inducing self-orientation of metalloproteins in solution, we have studied the complex of the 75-amino-acid calcium-binding protein calbindin D-9k with one Ce(III) ion (CaCeCb). Backbone N-15-H-1 (1)J values have been determined for CaCeCb at two different magnetic fields. The above values showed a distinct dependence on the magnetic field, which is caused by the partial orientation of the molecule in solution. The difference in the values at the two magnetic fields provides structural constraints, which have been used to refine the structure of CaCeCb. The refined structure showed an improvement in terms of the number of residues falling in favored regions of the Ramachandran plot. The comparison of the molecular magnetic susceptibility tensor, obtained from the N-15-H-1 (1)J values, with the magnetic susceptibility tensor of the metal, obtained from pseudocontact shifts, showed that the orientation of the molecule in solution is mainly determined by the Ce(III) ion. This paper shows that Ce(III), like low-spin Fe(III) in hemoproteins, is sufficiently magnetically anisotropic to induce self-orientation to an extent which can be exploited for solution structure determination. (C) 2001 Academic Press.
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页码:23 / 30
页数:8
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