[Preparation of Transmembrane Fragments Growth Hormone Receptor GHR in a Cell-Free Expression System for Structural...

Growth hormone somatotropin and its membrane receptor GHR, belonging to a superfamily of the type I receptors possessing tyrosine kinase activity, are involved in the intercellular signal transduction cascade and regulate a number of important physiological and pathological processes in humans. Binding with somatotropin triggers a transition of GHR between two alternative dimer states, resulting in an allosteric activation of JAK2 tyrosine kinase in the cell cytoplasm. Transmembrane domain of GHR directly involved in this complex conformational transition. It has presumably two dimerization interfaces corresponding to the "unliganded" and the active state of GHR. In order to study the molecular basis of biochemical signal transduction mechanism across the cell membrane, we have developed an efficient cell-free production system of a TM fragment of GHR, which contains its TM domain flanked by functionally important juxtamembrane regions (GHRtm residues 254-298). The developed system allows to obtain -1 mg per 1 ml of reaction mixture of 13C- and 15N-isotope-labeled protein for structural and dynamic studies of the GHR TM domain dimerization in the membrane-mimicking medium by high-resolution heteronuclear NMR spectroscopy.