University of Chicago MRSEC: Seed 1

1. Seed Project: Efficient enzymatic method to attach nanomaterials to live cells University of Chicago MRSEC researcher, Jun Yin, and collaborators have developed an efficient enzymatic method for attaching nanomaterials covalently to biomolecules in live cells. Using a protein posttranslational enzyme– Sfp phosphopantetheinyl transferase, quantum dots (QDs) are specifically attached to cell surface proteins. A transferrin receptor was tagged with site-specific QD labels and the dynamics of receptor trafficking upon ligand binding were imaged to demonstrate the utility of the approach [1]. In addition, engineering the substrate specificity of the Sfp enzyme by directed evolution allows small molecule fluorophores and QDs to be conjugated to Coenzyme A analogs for protein labeling in cells. [2, 3] This technique is expected to allow site-specific imaging, but can also be used to induce specific cellular responses such as shape change. Work made possible through NSF MRSEC DMR-0213745 and DMR-0820054. Labeling of cell surface transferrin receptors by QD-CoA conjugates. QDs can be conjugated with various CoA analogues for protein labeling with an engineered Sfp enzyme. [1] "Enzyme catalyzed site-specific protein labeling and cell imaging with quantum dots," M. Sunbul, M. Yen, Y.K. Zou, J. Yin, Chem. Comm.,45, 5927-9 (2008). [2] "Catalytic turnover-based phage selection for engineering the substrate specificity of Sfp phosphoantetheinyl transferase," M. Sunbul, N.J. Marshall, and J. Yin, J. Mol. Bio., 387, 883-98 (2009). [3] "Phosphopantetheinyl transferase catalyzed site-specific protein labeling with ADP conjugated chemical probes," Y. Zou, and J. Yin, JACS, 131, 22, 7548-9 (2009). University of Chicago MRSEC: Seed 1