ABSTRACT
MOLECULAR MODELING TO FACILITATE PROTEIN CRYSTALLIZATION Victor Sivozhelezova,b, Eugenia Pechkovaa, and Claudio NicolinibaNanoworld Institute, Fondazione EL.B.A., University of Genoa Medical School, Italy bInstitute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia manuscript@ibf.unige.it
7.1 INTRODUCTIONProtein crystallography remains the principal method for solving atomic structures of proteins and their complexes, especially for large proteins whose structures are unattainable using nuclear magnetic resonance (NMR). Protein crystallization remains a bottleneck of the method, for either resistance of many proteins to crystallize or difficulty in obtaining well-diffracting crystals.In spite of considerable progress reached recently for improvement of crystallization by altering the phase state of proteins, such as Langmuir-Blodgett film assisted crystallization for soluble proteins (Pechkova and Nicolini, 2004) or lipidic cubic phase crystallization method for membrane proteins (Landau and Rosenbusch, 1996), the process of crystallization remains largely empirical, as evident from development of more and more expansive crystallization screens, which allow to quickly test large Synchrotron Radiation and Structural Proteomics Edited by Eugenia Pechkova and Christian Riekel Copyright © 2012 Pan Stanford Publishing Pte. Ltd. www.panstanford.com
numbers of solution conditions, which have previously been found to be useful for crystallization. From structural genomics initiatives, it follows that the success rate for producing X-ray quality crystals has been estimated to be within 20%–50% for those proteins that can be expressed in soluble form (Hui and Edwards, 2003; Fogg et al., 2006).It is becoming understood that, while proteins obey the general theories of crystallization (Chernov et al., 2004), there are details in protein crystallization beyond the scope of those theories (Dumetz et al., 2008). Such details are related to complex shapes and anisotropy of physicochemical properties of protein structures, in which small structural changes may cause large changes in phase behavior.Particularly, it was long known that hemoglobin, with a single mutation, shows a different crystallization behavior (Vekilov et al., 2002). It was also recently found that a single mutation of gamma-crystallin inverts the temperature dependence of solution/crystal phase transition, namely crystallization occurs upon elevation rather than decrease in temperature (McManus et al., 2007); see also comment in Thurston et al. (2007). In such cases, drastic differences in crystallization behavior are observed, but three-dimensional (3D) structures of the mutant proteins remain practically the same as the native ones.
