Article

Involvement of cysteine 306 and alanine 63 in the thermostability and oligomeric organization of glucose isomerase from Streptomyces sp. SK

Biologia (impact factor: 0.56). 04/2012; 64(5):845-851. DOI:10.2478/s11756-009-0155-y pp.845-851

ABSTRACT The implication of the original alanine 63 (Ala63) and the unique cysteine 306 (Cys306) residues in the thermostability of
the Streptomyces sp. SK glucose isomerase (SKGI) were investigated by site-directed mutagenesis and homology modelling. The Cys306 to Ala
mutation within SKGI dramatically affected its thermal stability by decreasing the half-life from 80 to 15 min at 90°C while
the Ala63 to Ser replacement shifted this half-life to 65 min. The electrophoretic analysis proves that the residue Cys306
participates in oligomerization of the SKGI. Its stabilizing role is materialized by hydrogen bonds established with arginines
at positions 284 and 259, as deduced from the constructed three-dimensional model. We have also shown that the presence of
an Ala63 instead of Ser63 seems to be more suitable for enzyme thermostability by maintaining hydrophobic pocket that contributes
to the protection of the enzyme active site.

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Keywords

constructed three-dimensional model
 
electrophoretic analysis proves
 
enzyme active site
 
enzyme thermostability
 
homology modelling
 
hydrogen bonds
 
original alanine 63
 
positions 284
 
Ser replacement
 
site-directed mutagenesis
 
SK glucose isomerase
 
SKGI
 
Streptomyces sp
 
thermal stability
 
thermostability
 
unique cysteine 306