Characterization of the plastid import reaction of the pea NADPH-protochlorophyllide oxidoreductase (POR)

• NADPH: protochlorophyllide (POR) is a vital enzyme in the biosynthesis of chlorophyl where it catalyzes the reduction of Pchlide into Chlide in a light-dependent manner. POR is nucleus-encoded and imported into the plastids where it is found at the inner membranes. Together with its substrate and the co-factor NADPH it forms a ternary complex which is needed for catalytical activity. The anomaly of a decreasing POR level during active chlorophyll synthesis was cleared with the discovery of two different POR proteins, POR-A and POR-B, in barley and Arabidopsis thaliana. During greening, POR-A is negatively regulated by light both at transcriptional and proteolytical levels. In addition, the import of POR-A, but not POR-B, has been suggestedto require Pchlide in order to be translocated into the plastid. In this respect, POR-A differs from other known nucleus-encoded plastid proteins, and as it appears, this requirements represents a novel and exclusive import characteristic. In pea, only one POR gene has been found indicating that the situation for the regulation of POR import and accumulation is far from clear. We here present a characterization of the import conditions of the pea POR, including the potentional role of Pchlide inthe translocation step.

Subject headings

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Keyword

NATURAL SCIENCES

NATURVETENSKAP

Publication and Content Type

ref (subject category)

kon (subject category)