Anti-oxidative effect of ribonuclease inhibitor by site-directed mutagenesis and expression in Pichia pastoris |
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Authors: | Wu Yu Cui Xiuyun Wang Jihong Zhao Peng Xu Yuefei and Zhao Baochang |
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Institution: | (1) College of Live Sciences, Liaoning Normal University, Dalian, 116029, China;(2) Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian, 116027, China |
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Abstract: | Human placental ribonuclease inhibitor (hRI) is an acidic protein of Mr∼50kDa with unusually high contents of leucine and
cysteine residues. It is a cytosolic protein that protects cells from the adventitious invasion of pancreatic-type ribonuclease.
hRI has 32 cysteine residues, and the oxidative formation of disulfide bonds from those cysteine residues is a rapid cooperative
process that inactivates hRI. The most proximal cysteine residues in native hRI are two pairs that are adjacent in sequence.
In the present aork, two molecules of alanine substituting for Cys328 and Cys329 were performed by site-directed mutagenesis.
The site-mutated RI cDNA was constructed into plasmid pPIC9K and then transformed Pichia pastoris GS115 by electroporation. After colony screening, the bacterium was cultured and the product was purified with affinity chromatography.
The affinity of the recombinant human RI with double site mutation was examined for RNase A and its anti-oxidative effect.
Results indicated that there were not many changes in the affinity for RNase A detected when compared with the wild type of
RI. But the capacity of anti-oxidative effect increased by 7∼9 times. The enhancement in anti-oxidative effect might be attributed
to preventing the formation of disulfide bond between Cys328 and Cys329 and the three dimensional structure of RI was thereby
maintained.
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Translated from HEREDITAS, 2005, 27(2) 译自: 遗传,2005,27(2)] |
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Keywords: | ribonuclease inhibitor site-directed mutagenesis cysteine Pichia pastoris reactive oxygen species |
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