Ti Xiaonan, Tuzuki Nobuhiko, Tani Naoki, Isobe Minoru, Kai Hidenori
Insect Biochemistry and Biotechnology, Department of Biochemistry and Biotechnology, United Graduate School of Agricultural Sciences, Tottori University, Koyama, Tottori 680-8553, Japan.
J Insect Physiol. 2005 Sep;51(9):1025-32. doi: 10.1016/j.jinsphys.2005.04.019. Epub 2005 Jun 23.
TIME is an ATPase that measures a time interval by exhibiting transitory burst activation in eggs of the silkworm, Bombyx mori L. PIN is a peptide that regulates the time measurement of TIME. To address the mode of action of PIN, interactions between TIME and PIN were investigated. First, TIME was mixed with PIN for various periods (days) at 25 degrees C. The longer TIME was mixed with PIN, the later the transitory burst activation of TIME ATPase activity occurred, while no such delay occurred at 5 degrees C. Second, the capacity of PIN to bind with TIME was measured at the two temperatures by fluorescence polarization. The binding interaction was much tighter (nearly 1000 times) at 25 degrees C than that at 4 degrees C. Because the log EC50 (in nM) at 4 degrees C was about 7, PIN must dissociate from TIME at low temperatures at the physiological concentration of TIME in eggs. Thus, TIME appears to be restructured into a time-measuring conformation by PIN at the high temperatures of summer, whereas the TIME-PIN complex would dissociate at the low temperatures of winter. This dissociation acts as the preliminary cue for the ATPase activity burst of TIME, which in turn causes the completion of diapause development and initiates new developmental programs.
TIME是一种ATP酶，它通过在家蚕（Bombyx mori L.）卵中表现出短暂的爆发性激活来测量时间间隔。PIN是一种调节TIME时间测量的肽。为了研究PIN的作用方式，对TIME和PIN之间的相互作用进行了研究。首先，将TIME与PIN在25摄氏度下混合不同时间（天）。TIME与PIN混合的时间越长，TIME ATP酶活性的短暂爆发性激活出现得越晚，而在5摄氏度时没有出现这种延迟。其次，通过荧光偏振在这两个温度下测量PIN与TIME结合的能力。在25摄氏度时的结合相互作用比在4摄氏度时紧密得多（近1000倍）。因为在4摄氏度时的log EC50（以nM为单位）约为7，在卵中TIME的生理浓度下，PIN在低温时必须从TIME上解离。因此，在夏季高温时，TIME似乎会被PIN重新构建成一种时间测量构象，而在冬季低温时，TIME-PIN复合物会解离。这种解离是TIME的ATP酶活性爆发的初步线索，进而导致滞育发育的完成并启动新的发育程序。
