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Mar. Drugs 2018, 16(11), 418; https://doi.org/10.3390/md16110418

Loss of Function in Zeaxanthin Epoxidase of Dunaliella tertiolecta Caused by a Single Amino Acid Mutation within the Substrate-Binding Site

1
Department of Life Science, College of Natural Sciences, Hanyang University, Seoul 04763, Korea
2
Eugene Biotech Co. Ltd., Daejeon 34051, Korea
3
School of Life Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea
4
Research Institute of Natural Sciences, Hanyang University, Seoul 04763, Korea
*
Author to whom correspondence should be addressed.
Received: 14 October 2018 / Revised: 21 October 2018 / Accepted: 26 October 2018 / Published: 1 November 2018
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Abstract

The zea1 mutant of marine microalga Dunaliella tertiolecta accumulates zeaxanthin under normal growth conditions, and its phenotype has been speculated to be related to zeaxanthin epoxidase (ZEP). In this study, we isolated the ZEP gene from both wild-type D. tertiolecta and the mutant. We found that the zea1 mutant has a point mutation of the 1337th nucleotide of the ZEP sequence (a change from guanine to adenine), resulting in a change of glycine to aspartate in a highly conserved region in the catalytic domain. Similar expression levels of ZEP mRNA and protein in both wild-type and zea1 were confirmed by using qRT-PCR and western blot analysis, respectively. Additionally, the enzyme activity analysis of ZEPs in the presence of cofactors showed that the inactivation of ZEP in zea1 was not caused by deficiency in the levels of cofactors. From the predicted three-dimensional ZEP structure of zea1, we observed a conformational change on the substrate-binding site in the ZEP. A comparative analysis of the ZEP structures suggested that the conformational change induced by a single amino acid mutation might impact the interaction between the substrate and substrate-binding site, resulting in loss of zeaxanthin epoxidase function. View Full-Text
Keywords: zeaxanthin epoxidase; protein structure modeling; marine microalga; Dunaliella tertiolecta zeaxanthin epoxidase; protein structure modeling; marine microalga; Dunaliella tertiolecta
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Kim, M.; Kang, J.; Kang, Y.; Kang, B.S.; Jin, E. Loss of Function in Zeaxanthin Epoxidase of Dunaliella tertiolecta Caused by a Single Amino Acid Mutation within the Substrate-Binding Site. Mar. Drugs 2018, 16, 418.

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