Interhelical interactions between D92 and C218 in the cytoplasmic domain regulate proton uptake upon N-decay in the proton transport of Acetabularia rhodopsin II
Interhelical interactions between D92 and C218 in the cytoplasmic domain regulate proton uptake upon N-decay in the proton transport of Acetabularia rhodopsin II
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细胞质结构域中 D92 和 C218 之间的螺旋间相互作用调节 Acetabularia 视紫红质 II 质子运输中 N 衰变时的质子摄取
DOI：
10.1016/j.jphotobiol.2018.04.012
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Kamo Naoki
中科院分区：
文献类型：
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作者：
Tamogami Jun;Kikukawa Takashi;Ohkawa Keisuke;Ohsawa Noboru;Nara Toshifumi;Demura Makoto;Miyauchi Seiji;Kimura-Someya Tomomi;Shirouzu Mikako;Yokoyama Shigeyuki;Shimono Kazumi;Kamo Naoki
Acetabularia rhodopsin II （ARII或Ace2）是在巨大的单细胞海洋藻类Acetabularia acetabulum中发现的一种向外发光的藻类质子泵，在其通道的细胞质（CP）侧具有独特的性质。在暗态下，ARII的x射线晶体结构表明c218arii和D92ARII之间形成了螺旋间氢键，后者是Schiff碱的内部质子供体（Wada et al., 2011）。在本报告中，我们研究了C218ARII位置的两个突变体的光循环：c218aarii破坏了与D92ARII的相互作用，c218sarii可能形成更强的氢键。与野生型泵相比，两种突变体都表现出较慢的光循环。加上光循环前半部分光产物的一些动力学变化，这些替换导致了光循环后半段N-to-O转变的特定延迟。此外，使用ph敏感的氧化铟锡电极测量闪光诱导的质子摄取和释放，揭示了质子摄取的伴随延迟。这些观察结果有力地表明，c218arii和d92arii之间的天然弱氢键对于n衰变过程中CP通道中质子的适当易位的重要性。讨论了d92arii - c218arii螺旋间氢键在ARII功能中的推测作用。
Acetabularia rhodopsin II (ARII or Ace2), an outward light-driven algal proton pump found in the giant unicellular marine alga Acetabularia acetabulum, has a unique property in the cytoplasmic (CP) side of its channel. The X-ray crystal structure of ARII in a dark state suggested the formation of an interhelical hydrogen bond between C218ARIIand D92ARII, an internal proton donor to the Schiff base (Wada et al., 2011). In this report, we investigated the photocycles of two mutants at position C218ARII: C218AARIIwhich disrupts the interaction with D92ARII, and C218SARIIwhich potentially forms a stronger hydrogen bond. Both mutants exhibited slower photocycles compared to the wild-type pump. Together with several kinetic changes of the photoproducts in the first half of the photocycle, these replacements led to specific retardation of the N-to-O transition in the second half of the photocycle. In addition, measurements of the flash-induced proton uptake and release using a pH-sensitive indium-tin oxide electrode revealed a concomitant delay in the proton uptake. These observations strongly suggest the importance of a native weak hydrogen bond between C218ARIIand D92ARIIfor proper proton translocation in the CP channel during N-decay. A putative role for the D92ARII-C218ARIIinterhelical hydrogen bond in the function of ARII is discussed.