Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India.
Center for Interdisciplinary Science, Tata Institute of Fundamental Research, Hyderabad 500107, India.
Sci Adv. 2020 Apr 3;6(14):eaay7919. doi: 10.1126/sciadv.aay7919. eCollection 2020 Apr.
Transient tunnels that assemble and disassemble to facilitate passage of unstable intermediates in enzymes containing multiple reaction centers are controlled by allosteric cues. Using the 140-kDa purine biosynthetic enzyme PurL as a model system and a combination of biochemical and x-ray crystallographic studies, we show that long-distance communication between ~25-Å distal active sites is initiated by an allosteric switch, residing in a conserved catalytic loop, adjacent to the synthetase active site. Further, combinatory experiments seeded from molecular dynamics simulations help to delineate transient states that bring out the central role of nonfunctional adaptor domains. We show that carefully orchestrated conformational changes, facilitated by interplay of dynamic interactions at the allosteric switch and adaptor-domain interface, control reactivity and concomitant formation of the ammonia tunnel. This study asserts that substrate channeling is modulated by allosteric hotspots that alter protein energy landscape, thereby allowing the protein to adopt transient conformations paramount to function.
变构调控因子控制着含有多个反应中心的酶中，为了使不稳定中间产物顺利通过而组装和解体的瞬态通道。我们以 140kDa 的嘌呤生物合成酶 PurL 为模型系统，结合生化和 X 射线晶体学研究，结果表明，~25Å 远端活性位点之间的长程通讯是由位于临近合成酶活性位点的保守催化环中的变构开关起始的。此外，组合实验通过分子动力学模拟进行播种，有助于描绘出瞬时状态，突出非功能衔接域的核心作用。我们表明，变构开关和衔接域界面处的动态相互作用的相互作用，有助于精心编排的构象变化，从而控制反应性和氨隧道的伴随形成。这项研究断言，变构热点通过改变蛋白质能量景观来调节底物通道，从而使蛋白质能够采用对功能至关重要的瞬态构象。
