Modeling of Biomolecular Systems Interactions, Dynamics, and Allostery: Bridging Experiments and Computations - September 10-14, 2014, Istanbul, Turkey

Modeling of Biomolecular Systems Interactions, Dynamics, and Allostery Poster Session II

78-POS Board 31 Study of the Interaction of the Extracellular Domain in the ErbB2-ErbB2homodimer and ErbB2-Trastuzumab by Hydrodynamic Properties and Computational Models Javier Ramos 1 , Juan Francisco Vega 1 , Victor L. Cruz 1 , Ping Hu 2 , Javier Cortes 3 , Javier Martinez-Salazar 1 . 1 Instituto de Estructura de la Materia, CSIC, Madrid, Spain, 2 Sino Biological, Inc, Beijing, China, 3 Vall D'Hebron University Hospital, Barcelona, Spain. The ErbB2 receptor is one of the four members of the epidermal growth factor (EGFR) family of receptor tyrosine kinases (RTK), which also includes ErbB1/EGFR, ErbB3 and ErbB4. ErbB2 overexpression is associated with poor prognosis of breast cancer patients. It is known that ErbB2 receptors can exist on the cell surface as monomers, homodimers and heterodimers with ErbB1 or ErbB3. It has been shown that trastuzumab antibody, an approved therapeutics for treatment of ErbB2-overexpresing breast cancer, blocks ErbB2 homodimer activity [1]. In our study, we use a recombinant extracellular domain of the ErbB2, which has a His-tag motif of 10 His residues at the C-terminal. We study the formation of the ErbB2 homodimer and ErbB2/trastuzumab complexes by means of a combination of experimental techniques, such as dynamic and static light scattering as well as chromatography with tetradetection, along with simulations based on molecular dynamics and hydrodynamic models [2,3]. In this way, we are able to correlate the solution hydrodynamic data with macromolecular structural parameters. The experimental results indicate the presence of a variety of complexes between the ErbB2 extracellular domain and trastuzumab in aqueous phase. These complexes show a high degree of structural flexibility (measured by independent experiments in size- exclusion chromatography and dynamic light scattering), which is in agreement with our computational results. Under the experimental condition, our finding reveals the true dynamic features of the complexes in solution, an insight beyond what is known from the crystal structures. This flexibility does not allow us to perform 3D reconstruction imaging using TEM experiments [4]. References:

[1] Ghost R, et al. Cancer Res 2011, 71, 1871-1872 [2] Brandt J.P. et al. Biophysical J. 2010, 99, 905-913 [3] Brookes E. et al. Eur. Biophys J., 2010, 39(3), 423-435. [4] Vicente-Alique E. et al. Eur. Biophys. J. 2011, 40, 835-842.

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