{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,8,7]],"date-time":"2026-08-07T18:02:08Z","timestamp":1786125728344,"version":"build-2736575974"},"posted":{"date-parts":[[2026,8,5]]},"group-title":"Microbiology","reference-count":84,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T00:00:00Z","timestamp":1785888000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"award":["R35GM150794"],"award-info":[{"award-number":["R35GM150794"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]},{"award":["T32AI060546"],"award-info":[{"award-number":["T32AI060546"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,8,5]]},"abstract":"<jats:title>Summary<\/jats:title>\n                <jats:p>\n                  Inter-organellar communication is crucial for cellular function. Inside the cell, organelles interact with each other via membrane contact sites (MCSs). These structures mediate the close apposition of two organellar membranes to allow for the exchange of metabolites, ions and lipids. Most of what is known about MCSs comes only from a handful of well-studied metazoans, particularly yeast and mammals. Apicomplexans are parasites that drive human disease throughout the world. Yet, little is known about the makeup or function of their MCSs, leaving a gap in our understanding of how organelles communicate beyond conventional model eukaryotes. Here, we used a proximity biotinylation approach to map the surface proteome of three organelles in the model apicomplexan\n                  <jats:italic>Toxoplasma gondii<\/jats:italic>\n                  : the apicoplast\u2014a non-photosynthetic plastid found only in apicomplexans\u2014its single mitochondrion and the endoplasmic reticulum. By subtracting a cytosolic spatial reference, our high-stringency proteomic analysis uncovered candidate proteins localized simultaneously to multiple organellar surfaces suggesting their role as MCS components. We then validate our approach by characterizing a candidate involved in the association between the apicoplast and the mitochondrion. Overall, our findings provide a valuable approach to identify MCSs in apicomplexans and set the stage to apply our approach to other organelles in these pathogens.\n                <\/jats:p>\n                <jats:sec>\n                  <jats:title>Highlights<\/jats:title>\n                  <jats:list list-type=\"bullet\">\n                    <jats:list-item>\n                      <jats:p>\n                        Generation of surface proteomes for the apicoplast, mitochondrion, and ER in\n                        <jats:italic>Toxoplasma gondii<\/jats:italic>\n                      <\/jats:p>\n                    <\/jats:list-item>\n                    <jats:list-item>\n                      <jats:p>\n                        Mapping of the first endoplasmic reticulum and mitochondrial surface proteomes in\n                        <jats:italic>T. gondii<\/jats:italic>\n                      <\/jats:p>\n                    <\/jats:list-item>\n                    <jats:list-item>\n                      <jats:p>Identified novel membrane contact site candidate proteins<\/jats:p>\n                    <\/jats:list-item>\n                    <jats:list-item>\n                      <jats:p>Validated a membrane contact site candidate mediating mitochondrion\u2013apicoplast interactions<\/jats:p>\n                    <\/jats:list-item>\n                  <\/jats:list>\n                <\/jats:sec>","DOI":"10.64898\/2026.08.05.743015","type":"posted-content","created":{"date-parts":[[2026,8,6]],"date-time":"2026-08-06T04:50:32Z","timestamp":1785991832000},"source":"Crossref","is-referenced-by-count":0,"title":["A proximity biotinylation approach for the identification of membrane contact site proteins in\n                  <i>Toxoplasma gondii<\/i>"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-3540-7728","authenticated-orcid":false,"given":"Kaelynn V.","family":"Parker","sequence":"first","affiliation":[{"name":"Department of Cellular Biology, University of Georgia, Athens, GA, USA"},{"name":"Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4989-8918","authenticated-orcid":false,"given":"Diego","family":"Huet","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA, USA"},{"name":"Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026080710000739000_2026.08.05.743015v1.1","doi-asserted-by":"publisher","DOI":"10.1038\/s41467-019-09253-3"},{"key":"2026080710000739000_2026.08.05.743015v1.2","first-page":"7","article-title":"The functional universe of membrane contact sites","volume":"546","year":"2019","journal-title":"Nat. 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