This small family of proteins includes paralogues ChpX and ChpY in Synechococcus sp. PCC7942 and other cyanobacteria, associated with distinct NAD(P)H dehydrogenase complexes. These proteins collectively enable light-dependent CO2 hydration and CO2 uptake; loss of both blocks growth at low CO2 concentrations.
Jiyao W et al.(2023). "The conserved domain database in 2023.",