Structure-function-dynamics relationships in the peculiar Planktothrix PCC7805 OCP1: Impact of his-tagging and carotenoid type

Biochim Biophys Acta Bioenerg. 2022 Oct 1;1863(7):148584. doi: 10.1016/j.bbabio.2022.148584. Epub 2022 Jun 23.


The orange carotenoid protein (OCP) is a photoactive protein involved in cyanobacterial photoprotection. Here, we report on the functional, spectral and structural characteristics of the peculiar Planktothrix PCC7805 OCP (Plankto-OCP). We show that this OCP variant is characterized by higher photoactivation and recovery rates, and a stronger energy-quenching activity, compared to other OCP studied thus far. We characterize the effect of the functionalizing carotenoid and of his-tagging on these reactions, and identify the time scales on which these modifications affect photoactivation. The presence of a his-tag at the C-terminus has a large influence on photoactivation, thermal recovery and PBS-fluorescence quenching, and likewise for the nature of the carotenoid that additionally affects the yield and characteristics of excited states and the ns-s dynamics of photoactivated OCP. By solving the structures of Plankto-OCP in the ECN- and CAN-functionalized states, each in two closely-related crystal forms, we further unveil the molecular breathing motions that animate Plankto-OCP at the monomer and dimer levels. We finally discuss the structural changes that could explain the peculiar properties of Plankto-OCP.

Keywords: Cyanobacteria; Flash photolysis; Photosynthetic pigments; Structure function relationships; X-ray diffraction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism
  • Carotenoids / metabolism
  • Cyanobacteria* / metabolism
  • Fluorescence
  • Planktothrix*


  • Bacterial Proteins
  • Carotenoids