Plant cytochrome b(561), including the carbon monoxide oxygenase ACYB-1.
Cytochrome b(561), as found in plants, similar to the Arabidopsis thaliana ACYB-1 gene product, a cytochrome b561 isoform localized to the tonoplast. This protein might act as a ferric-chelate reductase, catalyzing the reduction of Fe(3+) to Fe(2+), and might be capable of trans-membrane electron transport from intracellular ascorbate to extracellular ferric chelates. It is assumed that this protein uses ascorbate as the electron donor. Belongs to the cytochrome b(561) family, which are secretory vesicle-specific electron transport proteins. Cytochromes b(561) are integral membrane proteins that bind two heme groups non-covalently, and may have six alpha-helical trans-membrane segments.