Sortase-Mediated Quantifiable Enzyme Immobilization on Magnetic Nanoparticles.

Protein immobilization has gained high interest in recent years for its valuable applications in life sciences involving drug delivery and protein arrays. Herein, we combine sortase-mediated protein immobilization with the versatility of magnetic nanoparticles and a sensitive GFP-based quantification system. Using this method, we successfully immobilized and quantified the amount of coupled enzymes by fluorescence spectroscopy and assessed their activity by kinetic measurements. We show that sortase-mediated coupling of enzymes enables preparation of biological samples with a high demand of purity as demonstrated by single-molecule FRET. Here, we report that sortase-mediated protein ligation allows both N- and C-terminal site-specific protein immobilization. Additionally, we demonstrate that sortase-mediated protein immobilization is suitable for direct protein immobilization from complex lysates. Direct immobilization from lysate allows study of enzyme functionality without the need of time-consuming enzyme purification, while magnetic nanoparticles permit easy addition and removal of coupled enzymes to and from a reaction mixture.