生理活性物質の標的蛋白質探索研究：アフィニティ樹脂に関する基盤研究例の紹介

抄録

Affinity chromatography matrices bearing bioactive compounds such as medicines, natural products, and toxins play an important role in the discovery of novel drug targets and the elucidation of drug mechanisms. Their effectiveness has been illustrated by finding of FKBP12, HDAC, Ref-13, and MDH as specific binding proteins of FK506 (1), Trapoxin, E-3330, and E-7070, respectively. The successful isolation of target proteins by affinity chromatography depends on the synthesis of polymeric resins that can bind to the cellular target with maximum selectivity and efficiency. Tubulin and actin often bind non-specifically to affinity chromatography resins, complicating research toward identifying the cellular targets of small molecules. Reduction of non-specific binding proteins is important for the success of such biochemical approaches. In order to develop strategies to circumvent this problem, we quantitatively investigated the binding of tubulin and actin to a series of affinity resins bearing fifteen variant ligands on three commercially available polymer supports. Non-specific protein binding was proportional to the hydrophobicity of the affinity resins and could be quantitatively correlated to the CLOGP values of the ligands, which are a measure of compound hydrophobicity. When compounds had CLOGP values greater than 1.5, (tubulin)=0.73*CLOGP-1.1, and (actin)=0.42*CLOGP-0.79 (n=7). Based on these studies, we designed a novel hydrophilic polyethyleneglycol (PEG) spacer for the conjugation of ligands to chromatography resins. As predicted by our binding algorithm, introduction of this spacer reduced the amount of non-specific protein binding in proportion to number of ethylene glycol units. If we have enough time, we additionally show a simple and versatile method for immobilization of ligands, termed "Chemical Shotgun", in which compounds are non-selectively immobilized on resins without the prior and boring design and synthesis of the derivative.