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Proc Natl Acad Sci U S A. 2016 Dec 20;113(51):14716-14721. doi: 10.1073/pnas.1616294113. Epub 2016 Dec 1.

Structural insights into the LCIB protein family reveals a new group of β-carbonic anhydrases.

Author information

1
School of Biological Sciences, Nanyang Technological University, Singapore 637551.
2
School of Agriculture and Food Science, Zhejiang A & F University, Hangzhou 311300, China.
3
School of Biological Sciences, Washington State University, Pullman, WA 99163.
4
School of Biological Sciences, Nanyang Technological University, Singapore 637551; ygao@ntu.edu.sg cajar@ntu.edu.sg.
5
Institute of Molecular and Cell Biology, A*STAR, Singapore 138673.

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.

KEYWORDS:

CO2-concentrating mechanism; LCIB; carbonic anhydrases; limiting-CO2 inducible protein; photosynthesis

PMID:
27911826
PMCID:
PMC5187666
DOI:
10.1073/pnas.1616294113
[Indexed for MEDLINE]
Free PMC Article

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