Evolution of a chimeric mitochondrial carbonic anhydrase through gene fusion in a haptophyte alga

• Published in: FEBS letters Vol. 596; no. 23; pp. 3051 - 3059
• Main Authors: Hirakawa, Yoshihisa, Hanawa, Yutaka, Yoneda, Kohei, Suzuki, Iwane
• Format: Journal Article
• Language: English
• Published: England 01.12.2022
• Subjects: algae; Carbon Dioxide - metabolism; carbonic anhydrase; Carbonic Anhydrases - genetics; Carbonic Anhydrases - metabolism; fusion protein; Gene Fusion; Haptophyta - genetics; Haptophyta - metabolism; haptophytes; mitochondria; Plants - metabolism; plastids; Recombinant Proteins - genetics; carbonic anhydrase; algae; haptophytes; fusion protein; mitochondria; plastids
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1002/1873-3468.14475

Carbonic anhydrases (CAs) are a universal enzyme family that catalyses the interconversion of carbon dioxide and bicarbonate, and they are localized in most compartments including mitochondria and plastids. Thus far, eight classes of CAs (α‐, β‐, γ‐, δ‐, ζ‐, η‐, θ‐ and ι‐CA) have been characterized. This study reports an interesting gene encoding a fusion protein of β‐CA and ι‐CA found in the haptophyte Isochrysis galbana. Recombinant protein assays demonstrated that the C‐terminal ι‐CA region catalyses CO2 hydration, whereas the N‐terminal β‐CA region no longer exhibits enzymatic activity. Considering that haptophytes generally have mitochondrion‐localized β‐CAs and plastid‐localized ι‐CAs, the fusion CA would show an intermediate stage in which mitochondrial β‐CA is replaced by ι‐CA in a haptophyte species. The present study reports a novel gene encoding two different classes of carbonic anhydrases (CAs) in a haptophyte alga. Its N‐ and C‐terminal regions carry a partial beta‐CA and a complete iota‐CA respectively. The fusion protein would show an evolutionary intermediate stage in which a mitochondrial beta‐CA is replaced by another class of CA.