A study of the protein-protein interactions in the phycocyanin monomer from sp PCC 6803 using a bacterial two-hybrid system.

Investigations into the intramolecular interactions of the native protein in solution are important to understand its structural stability as well as its potential uses in future applications. In this study, we used a bacterial two-hybrid system to investigate the interaction between the phycocyanin α and β subunits that form the phycocyanin monomer. Key amino acid residues responsible for the interaction between the subunits were identified, providing direct experimental evidence for the intramolecular interaction.

The active conformation of allophycocyanin from Spirulina platensis studied with spectroscopic analysis.

Allophycocyanin (APC) was purified from Spirulina platensis using hydroxylapatite chromatography and ion-exchange chromatography. Effects of solution pH on spectra of APC were studied. APC has an absorption maximum at 650 nm, and a shoulder at 620 nm.

Probing the pH sensitivity of R-phycoerythrin: investigations of active conformational and functional variation.

Crystal structures of phycobiliproteins have provided valuable information regarding the conformations and amino acid organizations of peptides and chromophores, and enable us to investigate their structural and functional relationships with respect to environmental variations. In this work, we explored the pH-induced conformational and functional dynamics of R-phycoerythrin (R-PE) by means of absorption, fluorescence and circular dichroism spectra, together with analysis of its crystal structure. R-PE presents stronger functional stability in the pH range of 3.