Psychrophile C-Phycocyanin

Abstract

C-Phycocyanin was purified from an alga isolated in the Antarctic in 1968 and grown since that time in our laboratory at 4 C. Certain of its spectroscopic and immunochemical properties were studied, along with detailed examinations of its chemical composition and quaternary structure. The hexamer-trmer equilibrium in the protein solution was studied as a function of pH, ionic strength, temperature, and susceptibility to certain small molecules. A major emphasis of the work was placed on a comparison of its protein-protein interactions with those of C-phycocyanins from both mesophilic and thermophilk algae.The chromoprotein C-phycocyanin, an accessory photosynthetic pigment found in blue-green and red algae, has been examined in this laboratory from a variety of algal species that grow at extremes of temperature, salinity, and acidity (2, 13-16, 18, 19). In particular, C-phycocyanin isolated from thermotolerant organisms has been studied in an effort to understand what modifications in phycocyanin structure could occur at the molecular level to adjust to this environmental extreme. Sedimentation velocity experiments have shown the interesting result that the aggregation of this protein is saliently changed when mesophilic and thermophilic C-phycocyanins are compared. To have a more complete view of this concept, it is desirable to obtain data on algae that thrive in very cold environments. Will such C-phycocyanin behave as those from the higher temperature organisms and display peculiar aggregation, or will the needs of life in the cold require no changes in these parameters?To determine whether survival at low temperature has an influence on protein properties, we report in the present work observations on aggregation behavior, amino acid composition, subunit structure, isoelectric point, absorption, fluorescence, and circular dichroism spectra, and immunochemical properties of Cphycocyanin isolated from the psychrophilic blue-green alga, Microcoleus vaginatus. These findings will be compared with those for C-phycocyanin from mesophilic and thermophilic algae. The general problem of biological adaptation to cold has been reviewed (7,12) (9) for carbohydrate. Allophycocyanin and phycoerythrin were also purified by ammonium sulfate fractionation from this alga. In general, the phycoerythrin precipitated with lower and allophycocyanin with higher ammonium sulfate concentrations than C-phycocyanin. Isoelectric focusing was performed on the 110 ml LKB Ampholine column (8101) with a sucrose gradient as a stabilizing system.The amino acid analysis employed the method of Spackman et al. (23) with 6 N HCI hydrolysis at 110 C. An analysis was also performed with 4 N methanesulfonic acid hydrolysis at 110 C for 22 h to ascertain the presence of tryptophan (22).Fluorescence spectra were obtained with a Baird-Atomic fluorescence spectrophotometer SF-1 at room temperature (23 C). An RCA model 4832 photomultiplier was used since its spectral response did not change significantly over the region 300 to 800 nm. The A i...

Thermokinetic stability of phycocyanin and phycoerythrin in food-grade preservatives

“…was found to degrade more than 80 % at higher temperatures ranging from 26 to 74°C (Chaiklahan et al 2012). Structurally, the conformation of PC has been reported to change into 23 % hexameric form at pH 5.5-6.0, while it persists up to 82 % in trimeric form at pH 7.0 (Kao et al 1975;Adams et al 1979;Chaiklahan et al 2012). This indicates that the trimeric form of PC is more stable at neutral pH which is mostly preferred for extraction of PBPs.…”

Functionalization of Nanostructured Hematite Thin‐Film Electrodes with the Light‐Harvesting Membrane Protein C‐Phycocyanin Yields an Enhanced Photocurrent

“…Similarly, the phycocyanin to be adsorbed on the hematite film was dissolved in a PBS buffer. The pI of phycocyanin is 4.64 30. In this case, the surface charge of the phycocyanin will be negative, since the pH of the surrounding environment is higher than that of pI.…”

Impact of incubation conditions on protein and C-Phycocyanin recovery from Arthrospira platensis post- pulsed electric field treatment

“…Furthermore, it has to be considered that the ionic strength of the initial buffer is considerably lower than the commonly used phosphate buffers at pH 6 for C-Phycocyanin extraction in other studies. At the pH ranges of 5.5-7.0 C-Phycocyanin can mostly be found in their stable trimeric or hexameric structures (Kao et al, 1975) (Adams et al, 1979). It is known that ionic strength influences the C-Phycocyanin aggregation state (Berns and MacColl, 1989), though various salts can affect the aggregation state of C-Phycocyanin in a different manner.…”