Methods

Methods

Most of the narrated information in this blog entry comes from the paper Wu et al. (2012) where X-ray crystallography was used to elucidate the structure of JDTic/kOR, nor-BNI/kOR and GNTI/kOR, ligand/receptor complexes.  The space group used was P2₁2₁2₁. The asymmetric unit consists of two receptors forming a parallel dimer, with an interface of 1,100 Å, involving helices I, II and VII. The R-value and R-free values obtained were 0.228 and 0.265 respectively. Unit cell descruptions are displayed in Figure 9. The orientation of both copies in the asymmetric unit differs in orientation by 60º and in fact, the slightly differing structural features between the two receptors in the asymmetric unit, for example like differences in the degree of tilt in the ECL2, are likely to be important clues as to the plasticity of these regions of the receptor. The authors also point out: ‘structural studies were carried out using an engineered human k-OR construct and crystallized in cholesterol-doped monoolein lipid cubic mesophase’. They also ensured that the pharmacological behavior of the isolated k-OR protein was similar to that of the native receptor expressed on HEK293T cells. For further detail on the methods used please refer to the primary literature.

Figure 9. Data on angles and lengths of the assymetric subunit from which the X-ray crystallographic data was interpreted from.

Unit Cell:
	Length [Å]	Angles [°]
	a = 54.90	α = 90.00
	b = 147.30	β = 90.00
	c = 205.29	γ = 90.00