An example for how crystallization at non-physiological pH (and non-physiological concentrations and non-physiological environmental) may influence behavior of the protein is the Botulinum A LC protease. Under normal conditions (upon endocytosis of a few molecules at best into the nerve cell), it works like a canonical serine protease, but at pH 4.6 it cleaves itself in a non-canonical fashion, i.e. with a loop resembling the target peptide running opposite direction. Later isoform structures solved at neutral pH showed normal, canonical protease activity.
http://www.ruppweb.org/cvs/br/Segelke_2004_PNAS_botulinum_neurotoxin.pdf BR From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Acoot Brett Sent: Saturday, October 27, 2012 8:01 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] inflluence of pH for crystallization on protein 3-D structure Dear All, A protein crystal can be got at pH 5 or 8, or a pH with much extreme value. What will be the relatively extreme pH value to get the crystal on the protein structure solved based on the crystal got? I mean usually we regard the physiological pH as 7. If a crystal was got at pH 5, the structure solved may be different from the protein structure at pH 7. But it seems there is rarely analysis on the discrepancy of the protein structures when publishing 3-D structure with the protein crystal got at relatively extreme pH. I am looking forward to getting your comment on it. Cheers, Acoot
