Biomaterial Database

Properties and N-terminal sequence of allophycocyanin from the unicellular rhodophyte Cyanidium caldarium. 1977

A S Brown, and R F Troxler

Allophycocyanin from the unicellular rhodophyte Cyanidium caldarium was purified by (NH4)2SO4 fractionation and ion-exchange chromatography on brushite (calcium phosphate) columns and on DEAE-Sephadex A-25 columns. The specific absorption coefficient (A0.1%1cm) at 650nm of purified allophycocyanin was 6.35 in 0.05M-potassium phosphate buffer, pH7.0. Absorption maxima of allophycocyanin occurred at 650, 618 (shoulder), 350 and 275 nm. Circular-dichroic spectra displayed positive-ellipticity bands at 658 and 630 nm and a major negative-ellipticity band at 340nm. Computer analysis of the circular-dichroic spectrum of allophycocyanin from 207 to 243 nm indicated 42% alpha-helix and 58% beta-form. The estimated molecular weight of purified allophycocyanin on calibrated Sephadex G-200 columns at pH7.0. was 196000. Electrophoretic examination of allophycocyanin on sodium dodecyl sulphate/polyacrylamide gels revealed a single band with apparent mol.wt. 16000. The presence of two polypeptide subunits, with nearly the same molecular weight, was revealed on polyacrylamide gels by using a modified electrophoresis buffer. Spectral analysis of the allophycocyanin subunits resolved by ion-exchange chromatography on Bio-Rex 70 columns indicated that a single phycocyanobilin chromophore was present on each polypeptide chain. Treatment of allophycocyanin with 8M-urea (pH3.0) and subsequent removal of urea by dialysis against water yielded a derivative phycobiliprotein with spectroscopic characteristics similar to those of phycocyanin. The original allophycocyanin spectrum was regenerated after incubation in phosphate buffer, pH7.0. Automated sequences analysis of the N-terminus of allophycocyanin showed that (a) the sequences of the two subunits were different from one another and were different from the subunits of phycocyanin from the same alga, (b) the subunits occurred in a molar ratio of 1:1 and (c) the sequences homology at the N-terminus among alpha- and beta-subunits of allophycocyanin from blue-green and red algae approached 90%.

UI	MeSH Term	Description	Entries
D010798	Phycocyanin	The metal-free blue phycobilin pigment in a conjugated chromoprotein of blue-green algae. It functions as light-absorbing substance together with chlorophylls.	C-Phycocyanin,C Phycocyanin
D010860	Pigments, Biological	Any normal or abnormal coloring matter in PLANTS; ANIMALS or micro-organisms.	Biological Pigments
D002621	Chemistry	A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D000461	Rhodophyta	Red algae whose color results from predominace of the red pigment (PHYCOERYTHRIN). However, if this pigment is destroyed, the algae can appear purple, brown, green, or yellow. Two important substances found in the cell walls of red algae are AGAR and CARRAGEENAN. Some rhodophyta are notable SEAWEED (macroalgae).	Algae, Red,Red Algae
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D013057	Spectrum Analysis	The measurement of the amplitude of the components of a complex waveform throughout the frequency range of the waveform. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Spectroscopy,Analysis, Spectrum,Spectrometry
D055598	Chemical Phenomena	The composition, structure, conformation, and properties of atoms and molecules, and their reaction and interaction processes.	Chemical Concepts,Chemical Processes,Physical Chemistry Concepts,Physical Chemistry Processes,Physicochemical Concepts,Physicochemical Phenomena,Physicochemical Processes,Chemical Phenomenon,Chemical Process,Physical Chemistry Phenomena,Physical Chemistry Process,Physicochemical Phenomenon,Physicochemical Process,Chemical Concept,Chemistry Process, Physical,Chemistry Processes, Physical,Concept, Chemical,Concept, Physical Chemistry,Concept, Physicochemical,Concepts, Chemical,Concepts, Physical Chemistry,Concepts, Physicochemical,Phenomena, Chemical,Phenomena, Physical Chemistry,Phenomena, Physicochemical,Phenomenon, Chemical,Phenomenon, Physicochemical,Physical Chemistry Concept,Physicochemical Concept,Process, Chemical,Process, Physical Chemistry,Process, Physicochemical,Processes, Chemical,Processes, Physical Chemistry,Processes, Physicochemical