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Yet, parasite actin filaments are short and unstable. Their kinetic characterization has been hampered by the lack of robust quantitative methods. Using a modified labeling method, we carried out thorough biochemical characterization of malaria parasite actin. In contrast to the isodesmic polymerization mechanism suggested for\n                    <jats:italic>Toxoplasma gondii<\/jats:italic>\n                    actin,\n                    <jats:italic>Plasmodium falciparum<\/jats:italic>\n                    actin I polymerizes\n                    <jats:italic>via<\/jats:italic>\n                    the classical nucleation-elongation pathway, with kinetics similar to canonical actins. A high fragmentation rate, governed by weak lateral contacts within the filament, is likely the main reason for the short filament length. At steady state,\n                    <jats:italic>Plasmodium<\/jats:italic>\n                    actin is present in equal amounts of short filaments and dimers, with a small proportion of monomers, representing the apparent critical concentration of ~0.1\u2009\u00b5M. The dimers polymerize but do not serve as nuclei. Our work enhances understanding of actin evolution and the mechanistic details of parasite motility, serving as a basis for exploring parasite actin and actin nucleators as drug targets against malaria and other apicomplexan parasitic diseases.\n                  <\/jats:p>","DOI":"10.1038\/s41598-017-11330-w","type":"journal-article","created":{"date-parts":[[2017,9,18]],"date-time":"2017-09-18T04:03:20Z","timestamp":1505707400000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":41,"title":["Apicomplexan actin polymerization depends on nucleation"],"prefix":"10.1038","volume":"7","author":[{"given":"Esa-Pekka","family":"Kumpula","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8359-9028","authenticated-orcid":false,"given":"Isa","family":"Pires","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Devaki","family":"Lasiwa","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Henni","family":"Piirainen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ulrich","family":"Bergmann","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Juha","family":"Vahokoski","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5236-7056","authenticated-orcid":false,"given":"Inari","family":"Kursula","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2017,9,22]]},"reference":[{"key":"11330_CR1","doi-asserted-by":"publisher","first-page":"667","DOI":"10.1016\/S0006-3495(01)75731-1","volume":"81","author":"D Sept","year":"2001","unstructured":"Sept, D. & McCammon, J. 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