Structural and spectroscopic characterization of HCP2

Maria Agustina Dominguez-Martin; Tomáš Polívka; Markus Sutter; Bryan Ferlez; Sigal Lechno-Yossef; Beronda L Montgomery; Cheryl A Kerfeld

doi:10.1016/j.bbabio.2019.03.004

Structural and spectroscopic characterization of HCP2

Biochim Biophys Acta Bioenerg. 2019 May 1;1860(5):414-424. doi: 10.1016/j.bbabio.2019.03.004. Epub 2019 Mar 15.

Authors

Maria Agustina Dominguez-Martin¹, Tomáš Polívka², Markus Sutter³, Bryan Ferlez¹, Sigal Lechno-Yossef¹, Beronda L Montgomery⁴, Cheryl A Kerfeld⁵

Affiliations

¹ MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
² Institute of Physics, Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic.
³ MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA; Environmental Genomics and Systems Biology and Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁴ MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA; Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
⁵ MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA; Environmental Genomics and Systems Biology and Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA. Electronic address: ckerfeld@lbl.gov.

PMID: 30880081
DOI: 10.1016/j.bbabio.2019.03.004

Abstract

The Helical Carotenoid Proteins (HCPs) are a large group of newly identified carotenoid-binding proteins found in ecophysiologically diverse cyanobacteria. They likely evolved before becoming the effector (quenching) domain of the modular Orange Carotenoid Protein (OCP). The number of discrete HCP families-at least nine-suggests they are involved in multiple distinct functions. Here we report the 1.7 Å crystal structure of HCP2, one of the most widespread HCPs found in nature, from the chromatically acclimating cyanobacterium Tolypothrix sp. PCC 7601. By purifying HCP2 from the native source we are able to identify its natively-bound carotenoid, which is exclusively canthaxanthin. In solution, HCP2 is a monomer with an absorbance maximum of 530 nm. However, the HCP2 crystals have a maximum absorbance at 548 nm, which is accounted by the stacking of the β1 rings of the carotenoid in the two molecules in the asymmetric unit. Our results demonstrate how HCPs provide a valuable system to study carotenoid-protein interactions and their spectroscopic implications, and contribute to efforts to understand the functional roles of this large, newly discovered family of pigment proteins, which to-date remain enigmatic.

Keywords: Carotenoid aggregates; Crystal structure; Cyanobacteria; Helical carotenoid protein; Photoprotection; Spectroscopic.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Bacterial Proteins / chemistry*
Canthaxanthin / chemistry*
Carrier Proteins / chemistry*
Crystallography, X-Ray
Cyanobacteria / chemistry*
Protein Domains
Protein Structure, Secondary

Substances

Bacterial Proteins
Carrier Proteins
Canthaxanthin