Oriented binding of the His6-tagged carboxyl-tail of the L-type Ca2+ channel α1-subunit to a new NTA-functionalized self-assembled monolayer

Oriented stable binding of functional proteins on surfaces is of fundamental interest for receptor/ligand studies in atomic force microscopy (AFM) and surface plasmon resonance (SPR) experiments. Here we have chosen the His(6)-tagged carboxyl-tail (C-tail) of the alpha(1C)-subunit of the L-type Ca2+ channel and calmodulin (CaM) as its cognitive partner as a model system to develop a new functional surface. Covalently attached self-assembled monolayers on ultraflat gold containing NTA-thiols to which the His(6)-tagged C-tail was bound and thiols with triethylene-glycol groups as matrix-thiols represented the system of choice. The topography of this surface was characterized using AFM; its ability to bind C-tail proteins oriented and stable was confirmed by SPR measurements and by complementary force spectroscopy experiments with a CaM4-construct covalently attached to the tip. The developed anchoring strategy can now be used to study receptor/ligand interactions in general applying force spectroscopy and SPR on His(6)-tagged proteins oriented immobilized onto this new NTA-functionalized self-assembled monolayer.