Chlorophyll-Binding Proteins of Higher Plants and Cyanobacteria

Translation and Co-translational Membrane Engagement of Plastid-encoded Chlorophyll-binding Proteins Are Not Influenced by Chlorophyll Availability in Maize

“…Interestingly, the PetD subunit of the cytochrome b 6 f complex was substantially reduced in the Zm -chlH-3 null mutant (∼10% of wild-type levels). Reduced levels of the cytochrome b 6 f complex were also observed in an Arabidopsis chlM mutant (Pontier et al, 2007), and may result from instability of the complex when its single chlorophyll is unavailable (Croce, 2012). The AtpB subunit of the ATP synthase and the large subunit of Rubisco (RbcL) accumulated to normal levels in the hypomorphic mutant but were reduced approximately four-fold in the Zm -chlH-3 null mutant; the reduction of these proteins is less severe than that of subunits of PSI, PSII, and the cytochrome b 6 f complex, consistent with the fact that the ATP synthase and Rubisco lack chlorophyll.…”

“…Compared to the sophisticated knowledge about the structure of the photosystems and the location of chlorophylls therein (Umena et al, 2011; Croce, 2012; Mazor et al, 2015), little is known about the coordination of apoprotein synthesis with chlorophyll availability. Although it is well established that chlorophyll binding proteins do not accumulate in the absence of chlorophyll (e.g., Klein et al, 1988a; Herrin et al, 1992; Eichacker et al, 1996), the relative contributions of increased protein instability and reduced protein synthesis remain unclear.…”

“…However, our analysis of ribosome footprints in separated membrane and soluble fractions showed that the position at which the nascent chlorophyll apoproteins engage the thylakoid membrane is not influenced by chlorophyll deficiency. This is perhaps unsurprising, given that none of the chlorophyll interaction sites is located upstream of the first transmembrane segment (UniProt annotations: PsaA (P04966), PsaB (P04967), PsbA (P48183), PsbD (P48184); and Croce, 2012), which comprises the signal that initially engages the membrane (Zoschke and Barkan, 2015). In line with that, the terminal chlorophyll synthesis enzymes and carrier were found to be associated with the thylakoid membrane, which would enable chlorophyll attachment to apoproteins only after membrane engagement of the nascent apoproteins (Wang and Grimm, 2015).…”

“…Additional reactions generate chlorophyll a and its descendant chlorophyll b . The majority of chlorophylls are bound by plastid-encoded proteins located in the cores of PSI (PsaA/B) and PSII (PsbA/B/C/D, also known as D1, CP47, CP43, and D2, respectively) and by nuclear-encoded proteins that make up the light harvesting complexes (LHC) (Umena et al, 2011; Croce, 2012; Mazor et al, 2015). …”

Identification of Genes Associated with Chlorophyll Accumulation in Flower Petals

“…The synthesis and activity of enzymes involved in the chlorophyll metabolic pathway are tightly regulated in a time-, development-, and tissue-specific manner. Chlorophylls are associated with chlorophyll-binding proteins of the photosystem I (PSI) and II (PSII) complexes [10] , [11] and accumulate in tissues where PSI and PSII are produced. A number of studies have been reported on the genetic elements that control chlorophyll accumulation in photosynthetic tissues [6] – [11] .…”