Open AccessPlastocyanin : Possible Significance of Quaternary Structure
Author(s) -
SIEGELMAN Mark H.,
RASCHED Ihab R.,
KUNERT KarlJosef.,
KRONECK Peter,
BÖGER Peter
Publication year - 1976
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1976.tb10281.x
Subject(s) - isoelectric point , plastocyanin , chemistry , spinach , dimer , isoelectric focusing , protein quaternary structure , monomer , polyacrylamide gel electrophoresis , gel electrophoresis , copper protein , amino acid , trimer , chromatography , copper , protein subunit , biochemistry , organic chemistry , enzyme , chloroplast , polymer , photosystem i , gene
Some properties of the blue copper protein plastocyanin from the green alga Scenedesmus have been investigated and compared with that from spinach, including amino acid composition, isoelectric point and copper content. The protein from Scenedesmus contains two, that from spinach four copper atoms per molecular weight of 40000. A combination of sodium dodecylsulfate/polyacrylamide gel electrophoresis and quantification of sulfhydryl groups indicates a strong preference for a species composed of 4 polypeptide chains of identical amino acid composition representing the enzymically active entity. Due to various treatments the subunits of both plastocyanins are detected as either monomer species alone or as monomer and dimer in a molar ratio of 2 : 1 on sodium dodecylsulfate gels. The four ‐SH groups per molecule are of different reactivity: two ‐SH groups can be detected after destruction of the chromophore; two more (forming an S‐S bridge in the dimer) become evident after appropriate reduction. A KCN treatment for production of apoprotein is reported and the use of electrodialysis to improve incomplete apoprotein formation. These studies lend support to the proposal of a quaternary structure. Apoproteins were subjected to dodecylsulfate gel analysis, which proved to be an effective means of estimating both the extent of apoprotein formation and its reconstitution to the holoprotein.