The molecular interaction of 4'-iodo-4'-deoxydoxorubicin with Leu-55Pro transthyretin 'amyloid-like' oligomer leading to disaggregation

• Published in: Biochemical journal Vol. 351; no. Pt 1; pp. 273 - 279
• Main Authors: Sebastião, M P, Merlini, G, Saraiva, M J, Damas, A M
• Format: Journal Article
• Language: English
• Published: England 01.10.2000
• Subjects: Amino Acid Substitution - genetics; Amyloidosis - metabolism; Crystallization; Doxorubicin - analogs & derivatives; Doxorubicin - chemistry; Doxorubicin - metabolism; Doxorubicin - pharmacology; Humans; Iodine - metabolism; Leucine - genetics; Leucine - metabolism; Models, Molecular; Prealbumin - antagonists & inhibitors; Prealbumin - chemistry; Prealbumin - genetics; Prealbumin - metabolism; Proline - genetics; Proline - metabolism; Protein Binding - drug effects; Protein Structure, Secondary - drug effects; Thiazoles - metabolism; X-Ray Diffraction
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/0264-6021:3510273

The crystal structure of the amyloidogenic Leu-55Pro transthyretin (TTR) variant has revealed an oligomer structure that may represent a putative amyloid protofibril [Sebastião, Saraiva and Damas (1998) J. Biol. Chem. 273, 24715-24722]. Here we report biochemical evidence that corroborates the isolation of an intermediate structure, an 'amyloid-like' oligomer, which is most probably present in the biochemical pathway that leads to amyloid deposition and that was isolated by the crystallization of the Leu-55Pro TTR variant. 4'-Iodo-4'-deoxydoxorubicin (IDOX) is a compound that interacts with amyloid fibrils of various compositions and it has been reported to reduce the amyloid load in immunoglobulin light chain amyloidosis [Merlini, Ascari, Amboldi, Bellotti, Arbustini, Perfetti, Ferrari, Zorzoli, Marinone, Garini et al. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 2959-2963]. In this work, we observed that the monoclinic Leu-55Pro TTR crystals, soaked with IDOX, undergo rapid dissociation. Moreover, under the same conditions, the orthorhombic wild-type TTR crystals are quite stable. This is explained by the different TTR conformations isolated upon crystallization of the two proteins; while the Leu-55Pro TTR exhibits the necessary conformation for IDOX binding, the same structure is not present in the crystallized wild-type protein. A theoretical model concerning the interaction of Leu-55Pro TTR with IDOX, which is consistent with the dissociation of the amyloid-like oligomer, is presented. In this model the IDOX iodine atom is buried in a pocket located between the two beta-sheets of the Leu-55Pro TTR monomer with the IDOX aromatic-moiety long axis nearly perpendicular to the direction of the beta-sheets.