Chlorophyll and carotenoid binding in a simple red algal light-harvesting complex crosses phylogenetic lines

Abstract

The membrane proteins of peripheral light-harvesting complexes (LHCs) bind chlorophylls and carotenoids and transfer energy to the reaction centers for photosynthesis. LHCs of chlorophytes, chromophytes, dinophytes, and rhodophytes are similar in that they have three transmembrane regions and several highly conserved Chl-binding residues. All LHCs bind Chl a, but in specific taxa certain characteristic pigments accompany Chl a: Chl b and lutein in chlorophytes, Chl c and fucoxanthin in chromophytes, Chl c and peridinin in dinophytes, and zeaxanthin in rhodophytes. The specificity of pigment binding was examined by in vitro reconstitution of various pigments with a simple light-harvesting protein (LHCaR1), from a red alga (Porphyridium cruentum), that normally has eight Chl a and four zeaxanthin molecules. The pigments typical of a chlorophyte (Spinacea oleracea), a chromophyte (Thallasiosira fluviatilis), and a dinophyte (Prorocentrum micans) were found to functionally bind to this protein as evidenced by their participation in energy transfer to Chl a, the terminal pigment. This is a demonstration of a functional relatedness of rhodophyte and higher plant LHCs. The results suggest that eight Chl-binding sites per polypeptide are an ancestral trait, and that the flexibility to bind various Chl and carotenoid pigments may have been retained throughout the evolution of LHCs.

5 The origin of the dinoflagellate plastid

“…It is also possible that the relatively rich plastidassociated gene content in the nuclear genome partially explains the diversity of plastids and photosymbiotic associations that occur in dinoflagellates. Although one might expect that components of the photosynthetic apparatus would be unlikely to function in an unrelated plastid, in vitro reconstitution of LHC complexes with allochthanous pigments has demonstrated energy transfer in such heterogeneous complexes (Grabowski et al 2001). Another hypothesis is that the ability to transfer typically plastid-encoded genes to the nucleus documented here may allow dinoflagellates to rapidly transfer genes from novel endosymbionts.…”

Benefits of an Inclusive US Education System

“…The complex of seven polypeptides was regulated by light intensity and had common chlorophyll-binding sequences (53). Reconstitution experiments showed that the binding of chlorophylls and carotenoids crossed phylogenetic lines (32). When a recombinant LHC protein from P. cruentum was presented with extracts containing chlorophylls and carotenoids that this alga cannot synthesize (chlorophyll b, lutein, neoxanthin, violaxanthin-as in spinach) or with extracts from diatoms (chlorophyll c, fucoxanthin, diadinoxanthin), they were functionally incorporated with energy transfer to chlorophyll a.…”

Reversed-phase HPLC Determination of Chlorophyll a′ and Naphthoquinones in Photosystem I of Red Algae: Existence of Two Menaquinone-4 Molecules in Photosystem I of Cyanidium caldarium

“…Green algae and higher plants utilize only membrane-intrinsic Chl a/b complexes, LHC I and LHC II. The light-harvesting systems of red algae are known to be a transitional state from cyanobacteria to green plants, 12,13 and contain both phycobiliprotein and membrane-intrinsic LHC I (containing Chl a alone as the chlorophyllous pigment). 14,15 Hence, the pigment composition of red algae is of much interest to examine the universality of the existence of one Chl a′ molecule in P700.…”

“…The light-harvesting systems of red algae are known to be a transitional state from cyanobacteria to green plants, 12,13 and contain both phycobiliprotein and membrane-intrinsic LHC I (containing Chl a alone as the chlorophyllous pigment). 14,15 Hence, the pigment composition of red algae is of much interest to examine the universality of the existence of one Chl a′ molecule in P700.In view of this, we extended the pigment composition analysis to two red algae, a marine alga Porphyridium purpureum employed for many biochemical studies [12][13][14] and an alga living in an extreme environment, Cyanidium caldarium. 16…”

“…In view of this, we extended the pigment composition analysis to two red algae, a marine alga Porphyridium purpureum employed for many biochemical studies [12][13][14] and an alga living in an extreme environment, Cyanidium caldarium. 16 …”