title: Thylakoid luminal θ-carbonic anhydrase critical for growth and photosynthesis in the marine diatom Phaeodactylum tricornutum.
abstract: The algal pyrenoid is a large plastid body, where the majority of the CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) resides, and it is proposed to be the hub of the algal CO2-concentrating mechanism (CCM) and CO2 fixation. The thylakoid membrane is often in close proximity to or penetrates the pyrenoid itself, implying there is a functional cooperation between the pyrenoid and thylakoid. Here, GFP tagging and immunolocalization analyses revealed that a previously unidentified protein, Pt43233, is targeted to the lumen of the pyrenoid-penetrating thylakoid in the marine diatom Phaeodactylum tricornutum The recombinant Pt43233 produced in Escherichia coli cells had both carbonic anhydrase (CA) and esterase activities. Furthermore, a Pt43233:GFP-fusion protein immunoprecipitated from P. tricornutum cells displayed a greater specific CA activity than detected for the purified recombinant protein. In an RNAi-generated Pt43233 knockdown mutant grown in atmospheric CO2 levels, photosynthetic dissolved inorganic carbon (DIC) affinity was decreased and growth was constantly retarded; in contrast, overexpression of Pt43233:GFP yielded a slightly greater photosynthetic DIC affinity. The discovery of a θ-type CA localized to the thylakoid lumen, with an essential role in photosynthetic efficiency and growth, strongly suggests the existence of a common role for the thylakoid-luminal CA with respect to the function of diverse algal pyrenoids.
authors.affiliation: Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan;
authors.forename: Sae
authors.initials: S
authors.lastname: Kikutani
authors.affiliation: Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan;
authors.forename: Kensuke
authors.initials: K
authors.lastname: Nakajima
authors.affiliation: Muroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Muroran, Hokkaido 051-0013, Japan.
authors.forename: Chikako
authors.initials: C
authors.lastname: Nagasato
authors.affiliation: Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan;
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Tsuji
authors.affiliation: Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan;
authors.forename: Ai
authors.initials: A
authors.lastname: Miyatake
authors.affiliation: Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan; yusuke@kwansei.ac.jp.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Matsuda
mesh_terms: D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D057486:Carbon Cycle / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D017377:Diatoms / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005822:Genetic Vectors / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D010788:Photosynthesis / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D020524:Thylakoids / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure
chemical_list: D020418:Algal Proteins; D011993:Recombinant Fusion Proteins; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D002256:Carbonic Anhydrases
keywords: CGHR domain; CO2-concentrating mechanism; luminal carbonic anhydrase; marine diatom; pyrenoid