title: Arginine residues as stabilizing elements in proteins.
abstract: Site-specific substitutions of arginine for lysine in the thermostable D-xylose isomerase (XI) from Actinoplanes missouriensis are shown to impart significant heat stability enhancement in the presence of sugar substrates most probably by interfering with nonenzymatic glycation. The same substitutions are also found to increase heat stability in the absence of any sugar derivatives, where a mechanism based on prevention of glycation can no longer be invoked. This rather conservative substitution is moreover shown to improve thermostability in two other structurally unrelated proteins, human copper, zinc-superoxide dismutase (CuZnSOD) and D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Bacillus subtilis. The stabilizing effect of Lys----Arg substitutions is rationalized on the basis of a detailed analysis of the crystal structures of wild-type XI and of engineered variants with Lys----Arg substitution at four distinct locations, residues 253, 309, 319, and 323. Molecular model building analysis of the structures of wild-type and mutant CuZnSOD (K9R) and GAPDH (G281K and G281R) is used to explain the observed stability enhancement in these proteins. In addition to demonstrating that even thermostable proteins can lend themselves to further stability improvement, our findings provide direct evidence that arginine residues are important stabilizing elements in proteins. Moreover, the stabilizing role of electrostatic interactions, particularly between subunits in oligomeric proteins, is documented.
authors.affiliation: Protein Engineering Department, Plant Genetic Systems, Gent, Belgium.
authors.forename: N T
authors.initials: NT
authors.lastname: Mrabet
authors.forename: A
authors.initials: A
authors.lastname: Van den Broeck
authors.forename: I
authors.initials: I
authors.lastname: Van den brande
authors.forename: P
authors.initials: P
authors.lastname: Stanssens
authors.forename: Y
authors.initials: Y
authors.lastname: Laroche
authors.forename: A M
authors.initials: AM
authors.lastname: Lambeir
authors.forename: G
authors.initials: G
authors.lastname: Matthijssens
authors.forename: J
authors.initials: J
authors.lastname: Jenkins
authors.forename: M
authors.initials: M
authors.lastname: Chiadmi
authors.forename: H
authors.initials: H
authors.lastname: van Tilbeurgh
mesh_terms: D019747:Aldose-Ketose Isomerases; D001120:Arginine / Q000737:chemistry* / Q000235:genetics; D002238:Carbohydrate Epimerases / Q000737:chemistry / Q000235:genetics; D003001:Cloning, Molecular; D004789:Enzyme Activation; D004795:Enzyme Stability; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry / Q000235:genetics; D006031:Glycosylation; D006358:Hot Temperature; D006801:Humans; D008239:Lysine / Q000737:chemistry / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D015202:Protein Engineering / Q000379:methods; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013482:Superoxide Dismutase / Q000737:chemistry / Q000235:genetics; D014961:X-Ray Diffraction
chemical_list: D011994:Recombinant Proteins; D001120:Arginine; D013482:Superoxide Dismutase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase; D008239:Lysine