title: Chromophore composition of the phycobiliprotein Cr-PC577 from the cryptophyte Hemiselmis pacifica.
abstract: The cryptophyte phycocyanin Cr-PC577 from Hemiselmis pacifica is a close relative of Cr-PC612 found in Hemiselmis virescens and Hemiselmis tepida. The two biliproteins differ in that Cr-PC577 lacks the major peak at around 612 nm in the absorption spectrum. Cr-PC577 was thus purified and characterized with respect to its bilin chromophore composition. Like other cryptophyte phycobiliproteins, Cr-PC577 is an (αβ)(α'β) heterodimer with phycocyanobilin (PCB) bound to the α-subunits. While one chromophore of the β-subunit is also PCB, mass spectrometry identified an additional chromophore with a mass of 585 Da at position β-Cys-158. This mass can be attributed to either a dihydrobiliverdin (DHBV), mesobiliverdin (MBV), or bilin584 chromophore. The doubly linked bilin at position β-Cys-50 and β-Cys-61 could not be identified unequivocally but shares spectral features with DHBV. We found that Cr-PC577 possesses a novel chromophore composition with at least two different chromophores bound to the β-subunit. Overall, our data contribute to a better understanding of cryptophyte phycobiliproteins and furthermore raise the question on the biosynthetic pathway of cryptophyte chromophores.
authors.affiliation: Physiology of Microorganisms, Faculty for Biology and Biotechnology, Ruhr University Bochum, Universitätsstraße 150, 44780, Bochum, Germany.
authors.forename: Kristina E
authors.initials: KE
authors.lastname: Overkamp
authors.forename: Sina
authors.initials: S
authors.lastname: Langklotz
authors.forename: Marco
authors.initials: M
authors.lastname: Aras
authors.forename: Stefan
authors.initials: S
authors.lastname: Helling
authors.forename: Katrin
authors.initials: K
authors.lastname: Marcus
authors.forename: Julia E
authors.initials: JE
authors.lastname: Bandow
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hoef-Emden
authors.forename: Nicole
authors.initials: N
authors.lastname: Frankenberg-Dinkel
mesh_terms: D001664:Biliverdine / Q000031:analogs & derivatives / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D044785:Cryptophyta / Q000378:metabolism* / Q000502:physiology; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry; D013058:Mass Spectrometry; D008970:Molecular Weight; D052980:Phycobilins / Q000737:chemistry; D052979:Phycobiliproteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D010798:Phycocyanin / Q000737:chemistry; D021122:Protein Subunits / Q000737:chemistry; D020539:Sequence Analysis, Protein
chemical_list: D045342:Light-Harvesting Protein Complexes; D052980:Phycobilins; D052979:Phycobiliproteins; D021122:Protein Subunits; D010798:Phycocyanin; C011069:phycocyanobilin; C040381:mesobiliverdin; D001664:Biliverdine