Open AccessDetection of l ‐lactate in polyethylene glycol solutions confirms the identity of the active‐site ligand in a proline dehydrogenase structure
Author(s) -
Zhang Min,
Tanner John J.
Publication year - 2004
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444904003786
Subject(s) - polyethylene glycol , lactate dehydrogenase , peg ratio , chemistry , crystallization , proline , dehydrogenase , ligand (biochemistry) , biochemistry , ionic strength , escherichia coli , enzyme , stereochemistry , nuclear chemistry , amino acid , organic chemistry , aqueous solution , receptor , finance , economics , gene
Polyethylene glycol (PEG) is often used in protein crystallography as a low‐ionic‐strength precipitant for crystallization and as a cryoprotectant for low‐temperature data collection. Prompted by the discovery of an apparent l ‐lactate molecule bound in the active site of the Escherichia coli PutA proline dehydrogenase domain crystal structure, the l ‐lactate concentration of several PEG solutions was measured. 50%( w / v ) solutions of PEGs with molecular weight 3000, 4000 and 8000 contain millimolar levels of l ‐lactate. In contrast, l ‐lactate was not detected in solutions of PEG monomethyl ethers or PEG 3350. These results help to explain why l ‐lactate was present in the proline dehydrogenase domain crystal structure. This work also has implications for the crystallization of enzymes that bind l ‐lactate.