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Investigation on the crystal structure of proteins and their complexes in solution from combined TEM techniques and solubility measurements: the case of endo‐1,3(4)‐β‐glucanase
Author(s) -
Guyot Ferréol V,
Hagnerelle X,
Gaunand A,
Larquet E,
Caussette M,
Lindet B
Publication year - 2003
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.1233
Subject(s) - solubility , protein crystallization , aqueous solution , titration , oligomer , monomer , crystallography , chemistry , glucanase , transmission electron microscopy , crystal structure , salting out , crystal (programming language) , chromatography , materials science , crystallization , organic chemistry , polymer , enzyme , nanotechnology , programming language , computer science
Endo ‐1,3(4)‐β‐glucanase was crystallized from a crude extract of protein solution by addition of a salt A + , X − . Optical microscopy showed needle‐shaped polydisperse crystals with a mean size of 10 µm. Using transmission electron microscopy with specific settings allows one to characterize the ordered arrays of a thin protein crystal and to determine the parameters of the crystal lattice. The results suggest that the unit cell of a endo ‐1,3(4)‐β‐glucanase crystal may consist in the association of a given number of these proteins. Such oligomers have already been seen for other proteins. The solubility of endo ‐1,3(4)‐β‐glucanase in aqueous solution was determined for several X − concentrations using BCA assay (titration of the total protein in solution) and electrophoresis. The new data are in agreement with a new simple model based on equilibrium between the oligomer in solution and neutral and charged X − complexes of the protein in the monomer state. The model provides a new approach to the usual salting‐in/salting‐out description of protein solubility. Copyright © 2003 Society of Chemical Industry