Interactions of Chaperonin with a Weakly Active Anthranilate Synthase from the Aphid Endosymbiont <Emphasis Type="Italic">Buchnera aphidicola</Emphasis> |
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Authors: | Chia-Ying Huang Chi-Ying Lee Hsiao-Chen Wu Mei-Hwa Kuo Chi-Yung Lai |
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Institution: | (1) Department of Biology, National Changhua University of Education, 1 Jin Der Road, Changhua, 50007, Taiwan, Republic of China;(2) Department of Entomology, National Chung Hsing University, Taichung, 40227, Taiwan, Republic of China |
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Abstract: | The endosymbiotic bacterium Buchnera provides its aphid host with essential amino acids. Buchnera is typical of intracellular symbiotic and parasitic microorganisms in having a small effective population size, which is
believed to accelerate genetic drift and reduce the stability of gene products. It is hypothesized that Buchnera mitigates protein instability with an increased production of the chaperonins GroESL. In this paper, we report the expression
and functional analysis of trpE, a plasmid-borne fast-evolving gene encoding the tryptophan biosynthesis enzyme anthranilate synthase. We overcame the problem
of low enzyme stability by using an anthranilate synthase-deficient mutant of E. coli as the expression host and the method of genetic complementation for detection of the enzyme activity. We showed that the
Buchnera anthranilate synthase was only weakly active at the temperature of 26°C but became inactive at the higher temperatures of
32°C and 37°C and that the coexpression with chaperonin genes groESL of E. coli enhanced the function of the Buchnera enzyme. These findings are consistent with the proposed role of groESL in the Buchnera–aphid symbiosis. |
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