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Accueil > Départements > Biochimie, Biophysique et Biologie Structurale > Diana KIRILOVSKY : Mécanismes régulateurs chez les organismes photosynthétiques

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  • The paralogs to the C-terminal domain of the cyanobacterial OCP are carotenoid donors to HCPs.

    23 septembre, par Muzzopappa F, Wilson A, Yogarajah V, Cot S, Perreau F, Montigny C, Bourcier de Carbon C, Kirilovsky D
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    The paralogs to the C-terminal domain of the cyanobacterial OCP are carotenoid donors to HCPs.

    Plant Physiol. 2017 Sep 21;:

    Authors: Muzzopappa F, Wilson A, Yogarajah V, Cot S, Perreau F, Montigny C, Bourcier de Carbon C, Kirilovsky D

    Abstract
    The photoactive Orange Carotenoid Protein photoprotects cyanobacteria cells by quenching singlet oxygen and excess excitation energy. Its N-terminal domain (NTD) is the active part of the protein and the C-terminal domain (CTD) regulates the activity. Recently, the characteristics of a family of soluble carotenoid-binding proteins (Helical Carotenoid Proteins or HCPs), paralogs of NTD-OCP, were described. Bioinformatics studies also revealed the existence of genes coding for homologs of CTD. Here, we show that the latter genes encode carotenoid proteins (CTDHs). This family of proteins contains two subgroups with distinct characteristics. One CTDH of each clade was further characterized and proved to be very good singlet oxygen quenchers. When synthesized in E. coli or Synechocystis PCC 6803, CTDHs form dimers that share a carotenoid molecule and are able to transfer their carotenoid to apo-HCPs and apo-OCP. The CTDHs from clade 2 have a cysteine in position 103. A disulfide bond is easily formed between the monomers of the dimer preventing carotenoid transfer. This suggests that the transfer of the carotenoid could be redox regulated in clade 2 CTDH. We also demonstrate here that apo-OCPs and apo CTDHs are able to take the carotenoid directly from membranes, while HCPs are unable. HCPs need the presence of CTDH to become holo-proteins. We propose that in cyanobacteria the CTDHs are carotenoid donors to HCPs.

    PMID: 28935842 [PubMed - as supplied by publisher]