. Author manuscript; available in PMC: 2017 Jan 1.

Published in final edited form as: Biopolymers. 2016 Jan;105(1):43–49. doi: 10.1002/bip.22702

Table 1.

Experimentally observed shifts in pK_a (ΔpK_a) in protein-small molecule binding.

Protein	Ligand	Titratable group	ΔpK_a	PDB ID of free protein	PDB ID of complex
HIV-1 protease	Pepstatin	Asp25	>+2.2¹⁴	3HVP	1HPX
HIV-1 protease	Pepstatin	Asp25’	<−1.5¹⁴	3HVP	1HPX
HIV-1 protease	DMP-32	Asp25/Asp25’	+2.19¹⁵	1HHP	1QBS
Plasmepsin II	Pepstatin	Asp34/Asp214	+0.1¹⁶	1PFZ	1SME
Plasmepsin II	Pepstatin	His164	+1.5¹⁶	1PFZ	1SME
Chymotrypsin	N-Acetyl-_L-Pbhe-CF₃	His57	+3.3¹⁷	6GCH	6GCH
Xylanase	2FXb	Glu172	−2.5¹⁸	1BVV	1BVV
Hydroxynitrile lyase	Thiocyanate	His235	+5.5¹⁹	2YAS	2YAS
TSG-6	Hyaluronan	His4	+0.5²⁰	1O7B	1O7C
Galectin-1	β-Galactoside	His44/His52	+0.3²¹	1W6N	2ZKN