Using lanthanoid complexes to phase large macromolecular assemblies

• Published in: Journal of synchrotron radiation 2011-01, Vol.18 (1), p.74-78
• Main Authors: Talon, Romain, Kahn, Richard, Durá, M. Asunción, Maury, Olivier, Vellieux, Frédéric M. D., Franzetti, Bruno, Girard, Eric
• Format: Article
• Language: English
• Subjects: Aminopeptidases - chemistry; Archaeal Proteins - chemistry; Chemical Sciences; Coordination Complexes - chemistry; Crystallization; Crystallography, X-Ray - methods; Diffraction Structural Biology; experimental phasing; lanthanoid complexes; Lanthanoid Series Elements - chemistry; large macromolecular assemblies; Macromolecular Substances; Pyrococcus horikoshii - enzymology; Scattering, Radiation; TET aminopeptidase; X-Ray Diffraction
• ISSN: 1600-5775; 0909-0495; 1600-5775
• DOI: 10.1107/S0909049510036824

Lanthanoid ions exhibit extremely large anomalous X‐ray scattering at their LIII absorption edge. They are thus well suited for anomalous diffraction experiments. A novel class of lanthanoid complexes has been developed that combines the physical properties of lanthanoid atoms with functional chemical groups that allow non‐covalent binding to proteins. Two structures of large multimeric proteins have already been determined by using such complexes. Here the use of the luminescent europium tris‐dipicolinate complex [Eu(DPA)3]3− to solve the low‐resolution structure of a 444 kDa homododecameric aminopeptidase, called PhTET1‐12s from the archaea Pyrococcus horikoshii, is reported. Surprisingly, considering the low resolution of the data, the experimental electron density map is very well defined. Experimental phases obtained by using the lanthanoid complex lead to maps displaying particular structural features usually observed in higher‐resolution maps. Such complexes open a new way for solving the structure of large molecular assemblies, even with low‐resolution data.