{
  "abstract": "Thermophilic bacterial lipases must combine structural stability with the conformational flexibility required for interfacial activation, yet the local organization of their metal-binding sites remains incompletely understood. Here, we determined two X-ray crystal structures of the family I.5 lipase from Geobacillus kaustophilus (GkLip). The 2.47-[A] orthorhombic model contains a Ca2+ ion at the conserved metal-binding site, whereas the 2.30-[A] anisotropic triclinic model contains four non-equivalent protein chains in which no Ca2+ ion was modeled. GkLip retains the canonical /{beta}-hydrolase fold, the Ser114-Asp318-His359 catalytic triad, the Phe17/Gln115 oxyanion-hole region, an extended lid, and a conserved Zn2+-binding site. In the orthorhombic structure, Gly287, Glu361, Asp366, and Pro367 contribute to the Ca2+ coordination environment. Pro367 adopts a C{gamma}-endo pucker in the Ca2+-containing structure; three Ca2+-free chains also adopt the endo pucker, whereas one adopts a C{gamma}-exo pucker. The presence of both Pro367 pucker states in the Ca2+-free structure is consistent with calcium preferentially stabilizing a pre-existing, coordination-compatible conformation. This local organization is further supported by an Arg35-centered network of direct and water-mediated contacts. Comparison with the 94%-identical open G. thermocatenulatus lipase reveals substantial lid rearrangement despite strong conservation of the protein core. Together, these structures highlight localized conformational variability at the calcium-binding region within an otherwise highly conserved thermophilic lipase scaffold.",
  "abstract_shown": true,
  "affiliations": [
    "Koc University"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "name": "M. S. Eyerci"
    },
    {
      "name": "A. Tulek"
    },
    {
      "name": "F. I. Ozdemir"
    },
    {
      "name": "G. Sukur"
    },
    {
      "affs": [
        0
      ],
      "name": "H. Demirci"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5y7j5nhe20par.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.10.06.756949",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.10.06.756949v1.full",
  "id": "5y7j5nhe20par",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.10.06.756949v1",
  "language": null,
  "licence": "CC-BY-NC",
  "licence_label": "CC BY-NC",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "microbiology"
    ],
    [
      "openalex",
      "1312|Protein Structure and Dynamics"
    ]
  ],
  "openalex": "W7221047988",
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.10.06.756949v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-06",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5y7j5nhe20par.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:26:40Z",
      "native_id": "10.64898/2026.10.06.756949",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.10.06.756949v1"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "biorxiv:microbiology",
      "subfield": "microbiology"
    }
  ],
  "title": "Calcium-associated Pro367 ring puckering supports conformational selection in a thermophilic lipase",
  "title_text": "Calcium-associated Pro367 ring puckering supports conformational selection in a thermophilic lipase",
  "type": "preprint",
  "updated_at": "2026-10-30T12:26:40Z",
  "url": "https://research.draconitic.com/paper/5y7j5nhe20par",
  "venue": "bioRxiv",
  "versions": []
}