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<jats:title>Protons find a path</jats:title> <jats:p> Adenosine triphosphate (ATP) synthases are dynamos that interconvert rotational and chemical energy. Capturing the complete structure of these multisubunit membrane-bound complexes has been hindered by their inherent ability to adopt multiple conformations. Srivastava <jats:italic>et al.</jats:italic> used protein engineering to freeze mitochondrial ATP synthase from yeast in a single conformation and obtained a structure with the inhibitor oligomycin, which binds to the rotating c-ring within the membrane. Hahn <jats:italic>et al.</jats:italic> show that chloroplast ATP synthase contains a built-in inhibitor triggered by oxidizing conditions in the dark chloroplast. The mechanisms by which these machines are powered are remarkably similar: Protons are shuttled through a channel to the membrane-embedded c-ring, where they drive nearly a full rotation of the rotor before exiting through another channel on the opposite side of the membrane (see the Perspective by Kane). </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.aas9699">eaas9699</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.aat4318">eaat4318</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6389" page="600" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat6275">600</jats:related-article> </jats:p>

<jats:title>Integrating glucose and fat</jats:title> <jats:p> Consuming too much glucose makes you fat, but it is unclear how this conversion is mediated by the body. Glycolysis links to gene transcription via the essential coenzyme nicotinamide adenine dinucleotide in its oxidized state (NAD <jats:sup>+</jats:sup> ). Ryu <jats:italic>et al.</jats:italic> found that compartmentalized NAD <jats:sup>+</jats:sup> synthesis and consumption integrate glucose metabolism and adipogenic (fat-promoting) transcription during adipocyte differentiation (see the Perspective by Trefely and Wellen). Competition between the NAD <jats:sup>+</jats:sup> precursors—nuclear NMNAT-1 and cytosolic NMNAT-2—for their common substrate, nicotinamide mononucleotide, regulates the balance between nuclear NAD <jats:sup>+</jats:sup> synthesis for adipogenic gene regulation and cytosolic NAD <jats:sup>+</jats:sup> synthesis used in metabolism. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.aan5780">eaan5780</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6389" page="603" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat6663">603</jats:related-article> </jats:p>

<jats:title>Protons find a path</jats:title> <jats:p> Adenosine triphosphate (ATP) synthases are dynamos that interconvert rotational and chemical energy. Capturing the complete structure of these multisubunit membrane-bound complexes has been hindered by their inherent ability to adopt multiple conformations. Srivastava <jats:italic>et al.</jats:italic> used protein engineering to freeze mitochondrial ATP synthase from yeast in a single conformation and obtained a structure with the inhibitor oligomycin, which binds to the rotating c-ring within the membrane. Hahn <jats:italic>et al.</jats:italic> show that chloroplast ATP synthase contains a built-in inhibitor triggered by oxidizing conditions in the dark chloroplast. The mechanisms by which these machines are powered are remarkably similar: Protons are shuttled through a channel to the membrane-embedded c-ring, where they drive nearly a full rotation of the rotor before exiting through another channel on the opposite side of the membrane (see the Perspective by Kane). </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.aas9699">eaas9699</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.aat4318">eaat4318</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6389" page="600" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat6275">600</jats:related-article> </jats:p>

<jats:p>Who could have imagined the possibility of an inter-Korean Summit this year, let alone one between the United States and North Korea? Recent news that North Korea may suspend nuclear tests and dismantle its test site is a startling about-face, given the country's multitude of missile and nuclear weapons tests over the past decade. Those incidents increased tensions at a time when questions were being raised about the instruments, approaches, and mechanisms that nations collectively strive to use to rid the world of weapons of mass destruction. At the end of this month, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) will convene a symposium in Vienna to emphasize what brings real security to the world—negotiated agreements that are effectively verifiable and credibly enforceable. These include the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The issue is not whether such current institutions and instruments are failing, but rather, preserving their integrity and building further trust in and around them.</jats:p>