Thiol Redox Regulation of Plant ?-Carbonic Anhydrase.

ABSTRACT: ?-carbonic anhydrases (?CA) accelerate the equilibrium formation between CO2 and carbonate. Two plant ?CA isoforms are targeted to the chloroplast and represent abundant proteins in the range of >1% of chloroplast protein. While their function in gas exchange and photosynthesis is well-characterized in carbon concentrating mechanisms of cyanobacteria and plants with C4-photosynthesis, their function in plants with C3-photosynthesis is less clear. The presence of conserved and surface-exposed cysteinyl residues in the ?CA-structure urged to the question whether ?CA is subject to redox regulation. Activity measurements revealed reductive activation of ?CA1, whereas oxidized ?CA1 was inactive. Mutation of cysteinyl residues decreased ?CA1 activity, in particular C280S, C167S, C230S, and C257S. High concentrations of dithiothreitol or low amounts of reduced thioredoxins (TRXs) activated oxidized ?CA1. TRX-y1 and TRX-y2 most efficiently activated ?CA1, followed by TRX-f1 and f2 and NADPH-dependent TRX reductase C (NTRC). High light irradiation did not enhance ?CA activity in wildtype Arabidopsis, but surprisingly in ?ca1 knockout plants, indicating light-dependent regulation. The results assign a role of ?CA within the thiol redox regulatory network of the chloroplast.

SUBMITTER: Dreyer A 

PROVIDER: S-EPMC7463553 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature