[Seminar] A novel carotenoid binding protein in cyanobacterial photoprotection (C-OCP)

Seminar

Title: A novel carotenoid binding protein in cyanobacterial photoprotection (C-OCP)

Speaker: David Buhrke

Affiliation: Technical University Berlin

Host: Smilja Todorovic - Raman Spectroscopy of Metalloproteins

Abstract :
The photoswitchable orange carotenoid protein (OCP) is indispensable for cyanobacterial photopro- tection by quenching phycobilisome fluorescence upon photoconversion from the orange OCPo to the red OCPr form. Cyanobacterial genomes frequently harbor, besides genes for orange carotenoid proteins (OCPs), several genes encoding homologs of OCP’s N- or C-terminal domains (NTD, CTD). Unlike the well-studied NTD homologs, called Red Carotenoid Proteins (RCPs), the role of CTD homologs remains elusive. Expression of Synechocystis OCP-CTD in carotenoid-producing Escherichia coli yielded a violet-colored protein, termed C-OCP. C-OCP itself is a novel, dimeric carotenoid-binding protein, which can coordinate canthaxanthin and zeaxanthin, effectively quenches singlet oxygen and interacts with the Fluorescence Recovery Protein. Here, we employed several methods, including  Resonance Raman (RR) spectroscopy, to investigate the structure of the canthaxanthin cofactor in OCP and C-OCP and develop a structural model of the cofactor for this novel protein. Furthermore, we show how OCP can be reassembled from its functional domains and assign physiological roles to the multitude of C-OCP homologs in cyanobacteria.​