8QX5
Helical Carotenoid Protein 4 (HCP4) from Anabaena with bound Canthaxanthin
Summary for 8QX5
| Entry DOI | 10.2210/pdb8qx5/pdb |
| Descriptor | Orange carotenoid-binding domain-containing protein, beta,beta-carotene-4,4'-dione (3 entities in total) |
| Functional Keywords | photoprotection, soluble proteins, orange carotenoid protein, cyanobacteria, photosynthesis |
| Biological source | Cyanobacteriota (blue-green algae) |
| Total number of polymer chains | 2 |
| Total formula weight | 40017.75 |
| Authors | Sklyar, J.,Wilson, A.,Kirilovsky, D.,Adir, N. (deposition date: 2023-10-22, release date: 2024-04-03, Last modification date: 2024-04-10) |
| Primary citation | Sklyar, J.,Wilson, A.,Kirilovsky, D.,Adir, N. Insights into energy quenching mechanisms and carotenoid uptake by orange carotenoid protein homologs: HCP4 and CTDH. Int.J.Biol.Macromol., 265:131028-131028, 2024 Cited by PubMed Abstract: Photodamage to the photosynthetic apparatus by excessive light radiation has led to the evolution of a variety of energy dissipation mechanisms. A mechanism that exists in some cyanobacterial species, enables non-photochemical quenching of excitation energy within the phycobilisome (PBS) antenna complex by the Orange Carotenoid Protein (OCP). The OCP contains an active N-terminal domain (NTD) and a regulatory C-terminal domain (CTD). Some cyanobacteria also have genes encoding for homologs to both the CTD (CTDH) and the NTD (referred to as helical carotenoid proteins, HCP). The CTDH facilitates uptake of carotenoids from the thylakoid membranes to be transferred to the HCPs. Holo-HCPs exhibit diverse functionalities such as carotenoid carriers, singlet oxygen quenchers, and in the case of HCP4, constitutive OCP-like energy quenching. Here, we present the first crystal structure of the holo-HCP4 binding canthaxanthin molecule and an improved structure of the apo-CTDH from Anabaena sp. PCC 7120. We propose here models of the binding of the HCP4 to the PBS and the associated energy quenching mechanism. Our results show that the presence of the carotenoid is essential for fluorescence quenching. We also examined interactions within OCP-like species, including HCP4 and CTDH, providing the basis for mechanisms of carotenoid transfer from CTDH to HCPs. PubMed: 38521321DOI: 10.1016/j.ijbiomac.2024.131028 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.9 Å) |
Structure validation
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