The occurrence of eukaryotic type III glutamine synthetase in the marine diatom Chaetoceros compressum

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• 作者：Shigeharu Kinoshita ; Sayaka Isu ; Gen Kaneko ; Hiroshi Yamada ; Takeya Hara ; Yasuo Itoh ; Shugo Watabe
• 关键词：GS ; GSIII ; Molecular evolution ; Plankton
• 刊名：Marine Genomics
• 出版年：2009
• 出版时间：June 2009
• 年：2009
• 卷：2
• 期：2
• 页码：103-111
• 全文大小：2212 K

文摘

Glutamine synthetase (GS) has been described as one of the oldest functioning genes and thus a good molecular clock protein. GS is diverged into three distinct forms, type I (GSI), type II (GSII) and type III (GSIII), the last type of which is a member of the most recently discovered family among GSs and thus has been reported from a limited number of prokaryotes. In the present study, we determined the full-length sequence of GSIII from the marine diatom Chaetoceros compressum. The 3′ untranslated region of the diatom GSIII gene was composed of a polyadenylation signal followed by a poly (A)⁺ tail, clearly demonstrating that its mRNA is transcribed from the eukaryotic genome. We also screened available genome databases and identified full-length GSIII sequences from 5 eukaryotic species. These eukaryotic GSIIIs specifically contained regions A–D and a long additional sequence flanking region V toward the C-terminal site, both being specific to GSIII. Phylogenic analysis revealed that eukaryotic GSIIIs are not within a monophyletic relationship with the possible occurrence of lateral gene transfer in GSIII during evolution.