Total Chemical Protein Synthesis for the Determination of Novel X-ray Structures by Racemic Protein Crystallography

Abstract

Total synthesis of proteins by modern chemical ligation methods enables the ready preparation of high purity protein molecules of typical size (up to ∼300 amino acid residues). This in turn enables the preparation of mirror image D-protein molecules not found in nature. Use of a racemic protein mixture (i.e. D-protein+L-protein) greatly facilitates the formation of diffraction-quality crystals of otherwise recalcitrant proteins. Facilitated crystallization is also observed for quasi-racemic protein mixtures. Centrosymmetric crystals of racemic proteins diffract to high resolution and offer enhanced possibilities for structure solution by direct computational methods. Racemic protein crystallography has been successfully applied to a number of recalcitrant protein molecules, and has been used to determine the structure of a 35kDa {L-protein target/D-protein ligand} complex.KeywordsChemical protein synthesisX-ray crystallographyRacemic protein crystallizationQuasi-racematesDirect methods