Chromophore composition of the phycobiliprotein Cr-PC577 from the cryptophyte Hemiselmis pacifica

Photosynth Res. 2014 Dec;122(3):293-304. doi: 10.1007/s11120-014-0029-1. Epub 2014 Aug 19.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biliverdine / analogs & derivatives
  • Biliverdine / chemistry
  • Chromatography, High Pressure Liquid
  • Cryptophyta / metabolism*
  • Cryptophyta / physiology
  • Light-Harvesting Protein Complexes / chemistry
  • Mass Spectrometry
  • Molecular Weight
  • Phycobilins / chemistry
  • Phycobiliproteins / chemistry*
  • Phycobiliproteins / metabolism
  • Phycobiliproteins / physiology
  • Phycocyanin / chemistry
  • Protein Subunits / chemistry
  • Sequence Analysis, Protein

Substances

  • Light-Harvesting Protein Complexes
  • Phycobilins
  • Phycobiliproteins
  • Protein Subunits
  • Phycocyanin
  • phycocyanobilin
  • mesobiliverdin
  • Biliverdine