Crystallization and X-ray structure of full-length recombinant human butyrylcholinesterase

Human butyrylcholinesterase (BChE) has been shown to function as an endogenous scavenger of diverse poisons. BChE is a 340 kDa tetrameric glycoprotein that is present in human serum at a concentration of 5 mg l ^-1. The well documented therapeutic effects of BChE on cocaine toxicity and organophosphorus agent poisoning has increased the need for effective methods of producing recombinant therapeutic BChE. In order to be therapeutically useful, BChE must have a long circulatory residence time or associate as tetramers. Full-length recombinant BChE produced in Chinese hamster ovary (CHO) cells or human embryonic kidney cells has been shown to associate as monomers, with a shorter circulatory residence time than the naturally occurring tetrameric serum protein. Based on the preceding observation as well as the need to develop novel methodologies to facilitate the mass production of therapeutic recombinant BChE, studies have been initiated to determine the structural basis of tetramer formation. Towards these ends, full-length monomeric recombinant BChE has been crystallized for the first time. A 2.8 Å X-ray structure was solved in space group P42₁2, with unit-cell parameters a = b = 156, c = 146 Å.