title: Native Mass Spectrometry Analysis of Oligomerization States of Fluorescence Recovery Protein and Orange Carotenoid Protein: Two Proteins Involved in the Cyanobacterial Photoprotection Cycle.
abstract: The orange carotenoid protein (OCP) and fluorescence recovery protein (FRP) are present in many cyanobacteria and regulate an essential photoprotection cycle in an antagonistic manner as a function of light intensity. We characterized the oligomerization states of OCP and FRP by using native mass spectrometry, a technique that has the capability of studying native proteins under a wide range of protein concentrations and molecular masses. We found that dimeric FRP is the predominant state at protein concentrations ranging from 3 to 180 μM and that higher-order oligomers gradually form at protein concentrations above this range. The OCP, however, demonstrates significantly different oligomerization behavior. Monomeric OCP (mOCP) dominates at low protein concentrations, with an observable population of dimeric OCP (dOCP). The ratio of dOCP to mOCP, however, increases proportionally with protein concentration. Higher-order OCP oligomers form at protein concentrations beyond 10 μM. Additionally, native mass spectrometry coupled with ion mobility allowed us to measure protein collisional cross sections and interrogate the unfolding of different FRP and OCP oligomers. We found that monomeric FRP exhibits a one-stage unfolding process, which could be correlated with its C-terminal bent crystal structure. The structural domain compositions of FRP and OCP are compared and discussed.
authors.affiliation: Department of Chemistry, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Yue
authors.identifier: http://orcid.org/0000-0003-2324-0800
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Department of Biology, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Haijun
authors.initials: H
authors.lastname: Liu
authors.affiliation: Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Department of Biology, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Rafael G
authors.initials: RG
authors.lastname: Saer
authors.affiliation: Department of Chemistry, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Department of Biology, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Meyer
authors.affiliation: Department of Chemistry, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Veronica L
authors.initials: VL
authors.lastname: Li
authors.affiliation: Department of Chemistry, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Liuqing
authors.initials: L
authors.lastname: Shi
authors.affiliation: Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Department of Biology, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: King
authors.affiliation: Department of Chemistry, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Michael L
authors.identifier: http://orcid.org/0000-0003-1159-4636
authors.initials: ML
authors.lastname: Gross
authors.affiliation: Department of Chemistry, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Photosynthetic Antenna Research Center, Washington University in St. Louis , St. Louis, Missouri 63130, United States.|Department of Biology, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D013058:Mass Spectrometry / Q000379:methods*; D045524:Phycobilisomes / Q000378:metabolism; D011487:Protein Conformation; D055503:Protein Multimerization; D058767:Protein Unfolding; D015203:Reproducibility of Results; D046939:Synechocystis / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D045524:Phycobilisomes; C109473:orange carotenoid protein, Synechocystis