THE 2 MONOFUNCTIONAL DOMAINS OF OCTAMERIC FORMIMINOTRANSFERASE-CYCLODEAMINASE EXIST AS DIMERS
THE 2 MONOFUNCTIONAL DOMAINS OF OCTAMERIC FORMIMINOTRANSFERASE-CYCLODEAMINASE EXIST AS DIMERS
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DOI：
10.1021/bi00033a006
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发表时间：
1995-08-22
期刊：
影响因子：
2.9
通讯作者：
MACKENZIE, RE
中科院分区：
文献类型：
--
作者：
MURLEY, LL;MACKENZIE, RE
甲亚氨基转移酶-环脱氨酶是一种双功能酶，排列为二聚体的环状四聚体，具有在催化位点之间有效引导聚谷氨酰化叶酸的能力。通过缺失诱变，我们证明每个亚基由一个 N 端转移酶活性结构域和一个 C 端脱氨酶活性结构域组成，由至少 8 个残基的接头序列分隔开。全长酶和两个分离的结构域已表达为 C 末端组氨酸标签蛋白。两个结构域自二聚化，为两种类型的亚基界面的存在提供了直接证据。结果表明，转移酶和脱氨酶活性都依赖于特定亚基界面的形成。由于在孤立的结构域之间未观察到通道效应，因此只有八聚体似乎能够在活性位点之间直接转移五谷氨酰化中间体。
Formiminotransferase - cyclodeaminase is a bifunctional enzyme arranged as a circular tetramer of dimers that exhibits the ability to efficiently channel polyglutamylated folate between catalytic sites. Through deletion mutagenesis we demonstrate that each subunit consists of an N-terminal transferase active domain and a C-terminal deaminase active domain separated by a linker sequence of minimally eight residues. The full-length enzyme and both isolated domains have been expressed as C-terminally histidine-tagged proteins. Both domains self-dimerize, providing direct evidence for the existence of two types of subunit interfaces. The results suggest that both the transferase and the deaminase activities are dependent on the formation of specific subunit interfaces. Because channeling is not observed between isolated domains, only the octamer appears able to directly transfer pentaglutamylated intermediate between active sites.