title: Effect of surface charge alteration on stability of L-asparaginase II from Escherichia sp.
abstract: Escherichia coli L-asparaginases have great significance in the treatment of leukemia. Consequently, there is considerable interest in engineering this enzyme for improving its stability. In this work, the effect of surface charge on the stability of the enzyme l-asparaginase II was studied by site-directed mutagenesis of the cloned ansB gene from Escherichia sp. Replacement of two positively charged residues (K139 and K207) on the surface loops with neutral and reverse charges resulted in altered thermo stability in designed variants. Neutral charge substitutions (K139A and K207A) retained greater tolerance and stability followed by negative charge substitutions (K139D and K207D) compared to control mutant K139R and wild enzyme. From the results, it was concluded that the optimization of surface charge contributed much to the thermal properties of proteins without affecting the structure.
authors.affiliation: Biotechnology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, India.
authors.forename: Jalaja
authors.initials: J
authors.lastname: Vidya
authors.affiliation: Biotechnology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, India.
authors.forename: Mrudula Vasudevan
authors.initials: MV
authors.lastname: Ushasree
authors.affiliation: Biotechnology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, India. Electronic address: ashokpandey56@yahoo.co.in.
authors.forename: Ashok
authors.initials: A
authors.lastname: Pandey
mesh_terms: D000818:Animals; D001215:Asparaginase / Q000737:chemistry* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001483:Base Sequence; D002417:Cattle; D003001:Cloning, Molecular; D004925:Escherichia / Q000201:enzymology*; D004926:Escherichia coli; D005243:Feces / Q000382:microbiology; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011489:Protein Denaturation; D055550:Protein Stability; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D001426:Bacterial Proteins; D001215:Asparaginase
keywords: Site-directed mutagenesis; Surface charge alteration; Thermal tolerance; l-Asparaginase