title: Structural insights into the LCIB protein family reveals a new group of β-carbonic anhydrases.
abstract: Aquatic microalgae have evolved diverse CO2-concentrating mechanisms (CCMs) to saturate the carboxylase with its substrate, to compensate for the slow kinetics and competing oxygenation reaction of the key photosynthetic CO2-fixing enzyme rubisco. The limiting CO2-inducible B protein (LCIB) is known to be essential for CCM function in Chlamydomonas reinhardtii To assign a function to this previously uncharacterized protein family, we purified and characterized a phylogenetically diverse set of LCIB homologs. Three of the six homologs are functional carbonic anhydrases (CAs). We determined the crystal structures of LCIB and limiting CO2-inducible C protein (LCIC) from C. reinhardtii and a CA-functional homolog from Phaeodactylum tricornutum, all of which harbor motifs bearing close resemblance to the active site of canonical β-CAs. Our results identify the LCIB family as a previously unidentified group of β-CAs, and provide a biochemical foundation for their function in the microalgal CCMs.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Shengyang
authors.initials: S
authors.lastname: Jin
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wunder
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.|School of Agriculture and Food Science, Zhejiang A & F University, Hangzhou 311300, China.
authors.forename: Desong
authors.initials: D
authors.lastname: Tang
authors.affiliation: School of Biological Sciences, Washington State University, Pullman, WA 99163.
authors.forename: Asaph B
authors.initials: AB
authors.lastname: Cousins
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Siu Kwan
authors.initials: SK
authors.lastname: Sze
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551; ygao@ntu.edu.sg cajar@ntu.edu.sg.
authors.forename: Oliver
authors.initials: O
authors.lastname: Mueller-Cajar
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551; ygao@ntu.edu.sg cajar@ntu.edu.sg.|Institute of Molecular and Cell Biology, A*STAR, Singapore 138673.
authors.forename: Yong-Gui
authors.initials: YG
authors.lastname: Gao
mesh_terms: D000388:Air; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry*; D002256:Carbonic Anhydrases / Q000737:chemistry*; D020134:Catalytic Domain; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D002736:Chloroplasts / Q000201:enzymology; D003001:Cloning, Molecular; D007477:Ions; D058086:Microalgae / Q000201:enzymology; D008968:Molecular Conformation; D009154:Mutation; D010788:Photosynthesis; D010940:Plant Proteins / Q000737:chemistry*; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000737:chemistry; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000737:chemistry
chemical_list: D007477:Ions; D010940:Plant Proteins; D011994:Recombinant Proteins; D014867:Water; D002245:Carbon Dioxide; D002244:Carbon; D002256:Carbonic Anhydrases; D015032:Zinc
keywords: CO2-concentrating mechanism; LCIB; carbonic anhydrases; limiting-CO2 inducible protein; photosynthesis