Site-specific labelling and cellular delivery of nanobodies

In collaboration with Prof. Leonhardt (LMU Munich) and Prof. Cardoso (TU Darmstadt) we develop new powerful methods to analyse and manipulate biochemical processes within living cells using functionalized nanobodies. Nanobodies are small, antigen binding proteins that remain active within the reductive milieu inside living cells. These properties give them a significant advantage for intracellular applications over conventional antibodies. Our long-term goal within this SPP 1623-funded project is to generate fluorescently labeled nanobodies functionalized with circular cell penetrating peptides (CPPs) for cellular uptake and caged amino acids for photoinducible activation. To install these functional units we use a combinatorial approach of intein expression, amber suppression and bioorthogonal reactions. In a recent proof of concept study, we were able to transport a functional full‑length protein, a GFP-CPP conjugate, to the cytosol and the nucleus of living cells. We will now use this concept to generate functional nanobodies that are able to penetrate through the cell’s plasma membrane and interfere with intracellular targets.