Title: Binding of red form of Orange Carotenoid Protein (OCP) to phycobilisome is not sufficient for quenching

Abstract

The Orange Carotenoid Protein (OCP) is responsible for photoprotection in many cyanobacteria. Absorption of blue light drives the conversion of the orange, inactive form (OCP^O) to the red, active form (OCP^R). Concomitantly, the N–terminal domain (NTD) and the C–terminal domain (CTD) of OCP separate, which ultimately leads to the formation of a quenched OCP^R–PBS complex. The details of the photoactivation of OCP have been intensely researched. Binding site(s) of OCP^R on the PBS core have also been proposed. Yet, the post–binding events of the OCP^R–PBS complex remain unclear. In this work, we demonstrate that PBS–bound OCP^R is not sufficient as a PBS excitation energy quencher. Using site–directed mutagenesis, we generated a suite of single point mutations at OCP Leucine 51 (L51) of Synechocystis 6803. Steady–state and time–resolved fluorescence analyses demonstrated that all mutant proteins are unable to quench the PBS fluorescence, owing to either failed OCP binding to PBS, or, if bound, an OCP–PBS quenching state failed to form. The SDS–PAGE and Western blot analysis support that the L51A (Alanine) mutant binds to the PBS and therefore belongs to the second category. We hypothesize that upon binding to PBS, OCP^R likely reorganizes and adopts a new conformational state (OCP^3rd) differentmore » than either OCP^O or OCP^R to allow energy quenching, depending on the cross–talk between OCP^R and its PBS core–binding counterpart.« less

Authors:

Lou, Wenjing ;

• Search DOE PAGES for author "Lou, Wenjing"
• Search DOE PAGES for ORCID "0000-0002-7511-1915"

Niedzwiedzki, Dariusz M. ;

• Search DOE PAGES for author "Niedzwiedzki, Dariusz M."
• Search DOE PAGES for ORCID "0000-0002-1976-9296"

Jiang, Ruidong J.; Blankenship, Robert E. ;

• Search DOE PAGES for author "Blankenship, Robert E."
• Search DOE PAGES for ORCID "0000-0003-0879-9489"

Liu, Haijun

• Search DOE PAGES for author "Liu, Haijun"
• Search DOE PAGES for ORCID "0000-0003-0537-0302"

Publication Date:

Sun Mar 01 00:00:00 EST 2020

Research Org.:

Washington Univ., St. Louis, MO (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division

OSTI Identifier:

1768117

Alternate Identifier(s):

OSTI ID: 1593978; OSTI ID: 1594183

Grant/Contract Number:  

FG02-07ER15902; SC0001035; DE–FG02–07ER15902; DE–SC0001035

Resource Type:

Published Article

Journal Name:

Biochimica et Biophysica Acta - Bioenergetics

Additional Journal Information:

Journal Name: Biochimica et Biophysica Acta - Bioenergetics Journal Volume: 1861 Journal Issue: 3; Journal ID: ISSN 0005-2728

Publisher:

Elsevier

Country of Publication:

Netherlands

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; Orange carotenoid protein; excitation energy quenching; site–directed mutagenesis; OCP–phycobilisome quenching complex