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

作者：Borgi Mohamed Ali; Rhimi Moez; Aghajari Nushin; Ben Ali Mamdouh; Juy Michel; Haser Richard; Bejar Samir^*

来源：Biologia, 2009, 64(5): 845-851.

DOI：10.2478/s11756-009-0155-y

• Streptomyces
• glucose isomerase
• site-directed mutagenesis
• thermostability
• oligomeric organization

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 90A degrees 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.

• 出版日期2009-10