Core Antenna Complexes, CP43 and CP47, of Higher Plant Photosystem II. Spectral Properties, Pigment Stoichiometry, and Amino Acid Composition

Abstract

The core antenna complexes of photosystem II, CP43 and CP47, were purified from two higher plants by anion-exchange chromatography, using a combination of the chaotropic agent UCIO4 and the nonionic detergent /3-dodecyl maltoside. The Qy transition was resolved at 48 K into two main bands near 682.3 and 671.5 nm for CP43, while the CP47 spectrum showed a more complex structure with main bands at 688, 681.2, 676, 670, 667, and 661 nm. Emission bands (77 K) were detected at 683 and 695 nm for CP43 and CP47, respectively. Fluorescence excitation spectra showed high efficiency of energy transfer between the different transitions of the chlorophylls and a somewhat lower efficiency from /3-carotene. The circular dichroism spectrum of CP47 indicated the presence of excitonic interactions between some chlorophylls. In contrast, CP43 showed a single negative circular dichroism band at 670 nm. The pigment content of the complexes was determined by both spectroscopic measurements and HPLC. Contents of 18 chlorophylls a and 5 /3-carotenes per CP43 polypeptide and 19 chlorophylls a and 3 /3-carotenes per CP47 polypeptide were found, using the methods of Lowry or Bradford for protein quantitation. When the protein concentration was determined from the amino acid analysis, 20 chlorophylls a and 5 /3-carotenes per CP43 and 21-22 chlorophylls a and 4 /3-carotenes per CP47 were obtained. Thus, a content of 46-48 chlorophylls a was obtained for the core complex, assuming 4-6 chlorophylls per reaction center, in agreement with the composition obtained experimentally using a highly purified oxygen-evolving core complex. This suggested that no pigments were lost during the purification procedure. Moreover, the amino acid analysis of the purified complexes revealed a high homology with the amino acid composition derived from the gene sequences reported for other higher plants.Photosystem (PS1) II is a membrane protein complex present in all oxygenic photosynthetic organisms. The smaller particle of PSII isolated so far, which is able to retain the primary processes of photosynthesis, i.e., charge separation, quinone reduction, and oxygen evolution, is a particle called the oxygenevolving core complex (OECC) (Ghanotakis & Yocum, 1986). This particle consists of eight main polypeptides, i.e., Di and D2, the a-and /3-subunits of cytochrome (Cyt) 6559, the psbl gene product of the reaction center (RC), the core antennae CP43 and CP47, and the 33-kDa extrinsic protein. Many * This work was supported by the Direccibn General de Investigacibn Cientifica y Tecnica (DGICYT, Grant PB92-0125). M.A. and G.M. are grateful to the Direccibn de Polltica Cientifica Gobierno Vasco and the CONAI-Diputacibn General Aragbn, respectively, for financial support.

Efficient Assembly of Photosystem II in Chlamydomonas reinhardtii Requires Alb3.1p, a Homolog of Arabidopsis ALBINO3

“…However, 77K fluorescence emission data indicate that the LHCII complexes present in ac29 are attached to PSII RCC complexes in vivo. PSII displays two fluorescence emission peaks at 695 nm and 686 nm corresponding to CP47 and CP43, respectively (Alfonso et al, 1994;Shen and Vermaas, 1994). In ac29, the CP47 peak was significantly higher as compared with the CP43 peak than in the wild type, indicating a higher energy transfer to CP47 than to CP43 and attachment of a higher number of antennae proteins to CP47 than to CP43.…”

Stoichiometrically Bound β-Carotene in the CytochromebfComplex of Oxygenic Photosynthesis Protects against Oxygen Damage

“…The ratio of the ellipticity peak of the ␤-carotene at 457 nm to that of the Chl a at 670 nm is 4.6:1. This ratio in the CP43 light-harvesting complex, which contains chlorophyll a and ␤-carotene in a ratio of 4:1, is 1:1 ␤-Carotene in Cytochrome b 6 f Complex (28). It is concluded that all of the bound ␤-carotene is bound in the complex in an asymmetric environment.…”

The N-Terminal Domain of Chlorophyllide a Oxygenase Confers Protein Instability in Response to Chlorophyll b Accumulation in Arabidopsis

“…The core complexes of photosystems I and II contain P700-chlorophyll a-protein complex and CP43/CP47 as internal light-harvesting antenna, respectively, and these complexes contain chlorophyll a and b-carotene as the photosynthetic pigments (Alfonso et al, 1994;Ben-Shem et al, 2003). On the other hand, depending on the photosynthetic organism, peripheral antenna complexes contain a variety of pigments, such as phycobilins, chlorophyll b, and fucoxanthin (Green and Durnford, 1996;Ting et al, 2002).…”