{
  "abstract": "The chloroplast F1Fo ATP synthase is a rotary motor that converts the light-driven proton-motive force into the chemical energy of ATP. The number of c-subunits in its rotor fixes the number of protons translocated per ATP formed, a fundamental parameter of bioenergetic systems. The reference spinach enzyme possesses fourteen c-subunits and a H+/ATP ratio of 4.67. Green algae additionally operate a carbon-concentrating mechanism that sustains CO2 fixation in water at a substantial cost in ATP, yet the structure of the algal motor, and whether its bioenergetic parameters differ from those of vascular plants, remains unresolved. Here, a 2.2 [A] structure of the ATP synthase of Chlamydomonas reinhardtii reveals that the enzyme carries a thirteen-membered c-ring, the first departure from c14 in a chloroplast, and with a lower predicted H+/ATP ratio of 4.33. Ordered waters trace a Grotthuss proton relay through the membrane, where an insulating triad separates the proton loading and unloading sites and couples flux to rotation. A single substitution in the redox switching {gamma}-subunit abolishes the contact with the catalytic {beta}-subunit that idles the enzyme in darkness in vascular plants. These unique features of the algal ATP synthase lower the H+/ATP cost of carbon fixation in the light and facilitate acetate metabolism in the dark.",
  "abstract_shown": true,
  "affiliations": [
    "University of Sheffield"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 10,
  "authors": [
    {
      "name": "K. Lorencik"
    },
    {
      "name": "S. Pintscher"
    },
    {
      "name": "K. Richardson"
    },
    {
      "name": "H. Takahashi"
    },
    {
      "name": "M. Proctor"
    },
    {
      "name": "M. Rawski"
    },
    {
      "name": "C. N. Hunter"
    },
    {
      "name": "A. Hitchcock"
    },
    {
      "name": "J. N. Blaza"
    },
    {
      "affs": [
        0
      ],
      "name": "M. P. Johnson"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9q1hjpwxatn6n.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.09.03.749062",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.09.03.749062v1.full",
  "id": "9q1hjpwxatn6n",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.09.03.749062v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "biochemistry"
    ],
    [
      "openalex",
      "1312|ATP Synthase and ATPases Research"
    ]
  ],
  "openalex": "W7210280782",
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.09.03.749062v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-03",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/9q1hjpwxatn6n.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:45Z",
      "native_id": "10.64898/2026.09.03.749062",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.09.03.749062v1"
    }
  ],
  "subjects": [
    {
      "field": "biochemistry",
      "origin": "openalex:1312|ATP Synthase and ATPases Research",
      "subfield": "molecular-biology"
    }
  ],
  "title": "A 13-subunit c-ring in the Chlamydomonas chloroplast ATP synthase lowers the H⁺/ATP cost of carbon fixation",
  "title_text": "A 13-subunit c-ring in the Chlamydomonas chloroplast ATP synthase lowers the H⁺/ATP cost of carbon fixation",
  "type": "preprint",
  "updated_at": "2026-10-30T12:19:45Z",
  "url": "https://research.draconitic.com/paper/9q1hjpwxatn6n",
  "venue": "bioRxiv",
  "versions": []
}