Chlorophyll Binding to Peptide Maquettes Containing a Retention Motif

Abstract

The motif Glu-X-X-His/Asn-X-Arg is conserved in the first and third membrane-spanning domains of all lightharvesting chlorophyll a/b-and a/c-binding proteins in chloroplasts. Molecular modeling of synthetic peptides containing the sequence Glu-Ile-Val-His-Ser-Arg, a motif found in the apoprotein of the major light-harvesting complex in plants, generated a loop structure formed by intrapeptide, electrostatic attraction between Glu and Arg. His, Asn, and charge-compensated Glu-Arg pairs are known ligands of the magnesium atom in chlorophyll. The prediction that this structure should bind two molecules of chlorophyll was confirmed experimentally with an assay based on fluorescence resonance energy transfer between peptides and chlorophyll a. Motifs with both potential ligands bound approximately two times the amount of chlorophyll as one in which His was replaced by Ala. These results support the conclusion that formation of this intermediate, within membranes of the envelope, is a crucial step in assembly of lightharvesting complexes and a mechanism that regulates import of the apoproteins into the chloroplast.

A role for chlorophyllide a oxygenase in the regulated import and stabilization of light-harvesting chlorophyll a / b proteins

“…Interestingly, this domain contains a binding maquette for Chl(ide) similar to that identified by Eggink and Hoober (29). Yamasato et al (30) proposed that this motif may provide a sensor for synthesis of Chl(ide) b in chloroplasts and observed that its deletion drastically affected the stability of the enzyme.…”

Perspectives for Photobiology in Molecular Solar Fuels

“…[94] A recent study demonstrated binding of a water-soluble bacteriochlorophyll derivative to a de novo designed haembinding four-helix bundle. [97] There are also other examples of Chl binding to synthetic peptides, [98][99][100] photo-active pigments such as Ru-pyridines, flavins and light-sensitive porphyrins [47,[101][102][103] (Fig. 2).…”

Discovery of a protein required for photosynthetic membrane assembly

“…His or Asn and charge-compensated Glu-Arg pairs are ligands of the Mg atom in chlorophyll. As expected, these retention motifs bind two molecules of chlorophyll (21). Because chlorophyll a binds more readily than chlorophyll b to the motifs, it is suggested that chlorophyll a is bound first and then oxidized to chlorophyll b by chlorophyllide a oxidase (CAO; ref.…”

“…2 (13,21,22). Structure analysis (23) and site-directed mutagenesis (24) have identified the sequence motifs Glu-X-X-His͞Asn-X-Arg as binding sites of chlorophyll in the first and third membranespanning domains of light-harvesting chlorophyll a͞b and a͞c proteins.…”