Table 3.

Histidine pKa values for mutants H27A, H30A, H180A in hPRL and H188A in hPRLr-ECD for unbound state. The predicted pKa’s were calculated using the corresponding bound structure taken from the corresponding X-ray structure of the complex. This is the reason why predicted pKa’s of the ligand are affected by mutations introduced at the receptor and vice versa.

	H27A		H30A		H180A		H188A
	Calc.	Exp.	Calc.	Exp.	Calc.	Exp.	Calc.	Exp.
HIS27.A			4.22	6.9	3.6	6.8	5.4	6.7
HIS30.A	4.7	6.5			6.2	6.7	3.6	6.3
HIS180.A	6.3	6.2	6.4	6.3			6.2	6.1
HIS188.B	6.8	7.7	6.8	7.7	6.8	7.7