Title: Synthetic OCP heterodimers are photoactive and recapitulate the fusion of two primitive carotenoproteins in the evolution of cyanobacterial photoprotection

Abstract

Summary The orange carotenoid protein ( OCP ) governs photoprotection in the majority of cyanobacteria. It is structurally and functionally modular, comprised of a C‐terminal regulatory domain ( CTD ), an N‐terminal effector domain ( NTD ) and a ketocarotenoid; the chromophore spans the two domains in the ground state and translocates fully into the NTD upon illumination. Using both the canonical OCP 1 from Fremyella diplosiphon and the presumably more primitive OCP 2 paralog from the same organism, we show that an NTD ‐ CTD heterodimer forms when the domains are expressed as separate polypeptides. The carotenoid is required for the heterodimeric association, assembling an orange complex which is stable in the dark. Both OCP 1 and OCP 2 heterodimers are photoactive, undergoing light‐driven heterodimer dissociation, but differ in their ability to reassociate in darkness, setting the stage for bioengineering photoprotection in cyanobacteria as well as for developing new photoswitches for biotechnology. Additionally, we reveal that homodimeric CTD can bind carotenoid in the absence of NTD , and name this truncated variant the C‐terminal domain‐like carotenoid protein ( CCP ). This finding supports the hypothesis that the OCP evolved from an ancient fusion event between genes for two differentmore » carotenoid‐binding proteins ancestral to the NTD and CTD . We suggest that the CCP and its homologs constitute a new family of carotenoproteins within the NTF 2‐like superfamily found across all kingdoms of life.« less

Authors:

Lechno‐Yossef, Sigal ^[1]; Melnicki, Matthew R. ^[2]; Bao, Han ^[1]; Montgomery, Beronda L. ^[1]; Kerfeld, Cheryl A. ^[3]

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+ Show Author Affiliations

1. Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Laboratory
2. Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Laboratory; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
3. Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Laboratory; Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Publication Date:

Mon May 15 00:00:00 EDT 2017

Research Org.:

Michigan State Univ., East Lansing, MI (United States). MSU-DOE Plant Research Laboratory

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)

OSTI Identifier:

1596270

Alternate Identifier(s):

OSTI ID: 1374081

Grant/Contract Number:  

FG02-91ER20021; IOS 1557324; DE‐FG02‐91ER20021

Resource Type:

Accepted Manuscript

Journal Name:

The Plant Journal

Additional Journal Information:

Journal Volume: 91; Journal Issue: 4; Journal ID: ISSN 0960-7412

Publisher:

Society for Experimental Biology

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; orange carotenoid protein; cyanobacteria; photoptotection; Fremyella diplosiphon; protein modularity; photoswitch