Retinoic acid receptor is a transcription factor in the cell nucleus that binds retinoic acid. The ligand binding domain of human gamma retinoic acid receptor, its complex with retinoic acid and its interaction with retinoic acid binding protein I, were studied by means of mass spectrometric methods. The pathway of delivering retinoic acid from donor to acceptor was monitored online. No ternary complex involving retinoic acid and the two proteins was observed, indicating that the transport of retinoic acid from retinoic acid binding protein I to its receptor may follow a two step mechanism, which involves dissociation of retinoic acid from the donor protein into the aqueous phase, followed by association with the acceptor.
retinoic acid receptor; retinoic acid binding protein; electrospray ionization mass spectrometry; noncovalent complex
