Bacterial expression of the water-soluble domain of lynx1, an endogenous neuromodulator of human nicotinic receptors

The membrane-associated protein Lynx1 is expressed in the human central nervous system and plays an important role in the regulation of the activity of nicotinic acetylcholine receptors. In the present study, ws-Lynx1 encoding the water-soluble domain of human Lynx1 was cloned and studied by heterological expression in E. coli. In milligram quantities, the ws-Lynx1 protein could only be obtained in cytoplasmic inclusion bodies of bacterial cells. To optimize the yield of ws-Lynx1 recombinant protein, a system was developed that allowed retrieving functionally active ws-Lynx1 from the inclusion bodies. After renaturation, the protein was characterized by mass spectrometry and by circular dichroism spectroscopy. ws-Lynx1 was shown to inhibit the binding of [¹²⁵I]-α-bungarotoxin to membranes from the electric organ of the Torpedo californica ray containing muscle-type nicotinic acetylcholine receptors (α1₂βγδ) in a competitive manner.