Uncoupling substrate delivery from export gate activation reveals distinct roles of the flagellar ATPase complex

Minamino, Tohru; Kinoshita, Miki; Tajimi, Yuki; Uchihashi, Takayuki; Namba, Keiichi

doi:https://doi.org/10.3389/fmicb.2026.1841110

Uncoupling substrate delivery from export gate activation reveals distinct roles of the flagellar ATPase complex

Minamino, Tohru; Kinoshita, Miki; Tajimi, Yuki et al.

Frontiers in Microbiology, 2026, 17, 99

アクセス数:184件（2026-10-11 12:39 集計）

固定URL: https://hdl.handle.net/11094/106070

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タイトル	Uncoupling substrate delivery from export gate activation reveals distinct roles of the flagellar ATPase complex
著者	NRID 1000020402993 1000020402993 ORCID 0000-0002-8175-1951 0000-0002-8175-1951 researchmap permalink tohru_minamino tohru_minamino Scopus Author ID 7006391123 7006391123 著者名 Minamino, Tohru
	NRID 1000030790985 1000030790985 ORCID 0000-0001-8679-3387 0000-0001-8679-3387 researchmap permalink miki_kinoshita miki_kinoshita Scopus Author ID 35310858600 35310858600 著者名 Kinoshita, Miki
	著者名 Tajimi, Yuki
	NRID 1000030326300 1000030326300 著者名 Uchihashi, Takayuki
	NRID 1000030346142 1000030346142 ORCID 0000-0003-2911-5875 0000-0003-2911-5875 researchmap permalink read0096830 read0096830 Scopus Author ID 7103162863 7103162863 著者名 Namba, Keiichi
キーワード等	ATPase complex
	flagellar type III secretion system
	FliH
	Flii
	FliJ
	ion coupling
	protein export
内容	Minamino Tohru, Kinoshita Miki, Tajimi Yuki, et al. Uncoupling substrate delivery from export gate activation reveals distinct roles of the flagellar ATPase complex. Frontiers in Microbiology 17, 99 (2026); https://doi.org/10.3389/fmicb.2026.1841110.
抄録	The bacterial flagellar type III secretion system (fT3SS) exports structural subunits required for flagellar assembly by coupling protein translocation to ion motive force across the cytoplasmic membrane. Efficient activation of the transmembrane export gate depends on a cytoplasmic ATPase complex composed of FliH, FliI, and FliJ, which are also involved in substrate delivery. However, how these proteins mechanistically integrate substrate delivery with gate activation remains unclear. Here, we uncoupled these two functions by cross-complementation analyses using ATPase components from the Na⁺-driven polar flagellum of Vibrio and the H⁺-driven flagellum of Salmonella. Despite low sequence identity, Vibrio FliJ complemented a Salmonella ΔfliJ mutant and restored Na+-independent protein export to a substantial extent, demonstrating a highly conserved mechanism of export gate activation. In contrast, Vibrio FliH and FliI exhibited interspecies incompatibility when expressed individually, and their co-expression in a Salmonella ΔfliH-fliI mutant supported protein export only under Na⁺-coupled conditions, consistent with the failure to activate the H⁺-driven export gate. Biochemical analyses revealed species-specific interactions between FliH and FliI, while high-speed atomic force microscopy showed that the Vibrio FliH-FliI complex retains the ability to assemble into ring-shaped structures. Together, these findings demonstrate that ATPase ring assembly and substrate delivery are mechanistically separable from export gate activation, revealing distinct and differentially conserved roles of the flagellar ATPase complex in coupling ATP hydrolysis to ion-driven protein export.
出版者	Frontiers Media SA
収録物名	Frontiers in Microbiology
巻(号)	17
ページ	99
刊行年月	2026-05-21
言語	英語
ハンドルURL	https://hdl.handle.net/11094/106070
eISSN	1664302X
関連情報 (isIdenticalTo)	DOI (出版社版) https://doi.org/10.3389/fmicb.2026.1841110
アクセス権	open access
権利情報	This article is licensed under a Creative Commons Attribution 4.0 International License.
出版タイプ	Version of Record
カテゴリ	学術雑誌論文 Journal Article

資源タイプ	学術雑誌論文
ローカル資源タイプ	学術雑誌論文
DCMI資源タイプ	text
DCTERMS.bibliographicCitation	Frontiers in Microbiology. 2026, 17, p. 99
DC.title	Uncoupling substrate delivery from export gate activation reveals distinct roles of the flagellar ATPase complex
DC.creator	Minamino, Tohru
	Kinoshita, Miki
	Tajimi, Yuki
	Uchihashi, Takayuki
	Namba, Keiichi
DC.publisher	Frontiers Media SA
DC.language' scheme='DCTERMS.RFC1766	英語
DC.type' scheme='DCTERMS.DCMIType	text
DCTERMS.issued' scheme='DCTERMS.W3CDTF	2026-05-21
DC.identifier	https://doi.org/10.3389/fmicb.2026.1841110
DC.subject	ATPase complex
	flagellar type III secretion system
	FliH
	Flii
	FliJ
	ion coupling
	protein export
DC.description	Minamino Tohru, Kinoshita Miki, Tajimi Yuki, et al. Uncoupling substrate delivery from export gate activation reveals distinct roles of the flagellar ATPase complex. Frontiers in Microbiology 17, 99 (2026); https://doi.org/10.3389/fmicb.2026.1841110.
DCTERMS.abstract	The bacterial flagellar type III secretion system (fT3SS) exports structural subunits required for flagellar assembly by coupling protein translocation to ion motive force across the cytoplasmic membrane. Efficient activation of the transmembrane export gate depends on a cytoplasmic ATPase complex composed of FliH, FliI, and FliJ, which are also involved in substrate delivery. However, how these proteins mechanistically integrate substrate delivery with gate activation remains unclear. Here, we uncoupled these two functions by cross-complementation analyses using ATPase components from the Na⁺-driven polar flagellum of Vibrio and the H⁺-driven flagellum of Salmonella. Despite low sequence identity, Vibrio FliJ complemented a Salmonella ΔfliJ mutant and restored Na+-independent protein export to a substantial extent, demonstrating a highly conserved mechanism of export gate activation. In contrast, Vibrio FliH and FliI exhibited interspecies incompatibility when expressed individually, and their co-expression in a Salmonella ΔfliH-fliI mutant supported protein export only under Na⁺-coupled conditions, consistent with the failure to activate the H⁺-driven export gate. Biochemical analyses revealed species-specific interactions between FliH and FliI, while high-speed atomic force microscopy showed that the Vibrio FliH-FliI complex retains the ability to assemble into ring-shaped structures. Together, these findings demonstrate that ATPase ring assembly and substrate delivery are mechanistically separable from export gate activation, revealing distinct and differentially conserved roles of the flagellar ATPase complex in coupling ATP hydrolysis to ion-driven protein export.
DC.rights	This article is licensed under a Creative Commons Attribution 4.0 International License.
DC.format	106070
citation_title	Uncoupling substrate delivery from export gate activation reveals distinct roles of the flagellar ATPase complex
citation_author	Minamino, Tohru
	Kinoshita, Miki
	Tajimi, Yuki
	Uchihashi, Takayuki
	Namba, Keiichi
citation_publisher	Frontiers Media SA
citation_language	英語
citation_date	2026-05-21
citation_journal_title	Frontiers in Microbiology
citation_volume	17
citation_firstpage	99
citation_doi	https://doi.org/10.3389/fmicb.2026.1841110
citation_public_url	https://hdl.handle.net/11094/106070

Uncoupling substrate delivery from export gate activation reveals distinct roles of the flagellar ATPase complex

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