Abstract
Phycocyanin complexes with "linker" polypeptides (Lundell, D. J., Williams, R. C., and Glazer, A. N. (1981) J. Biol. Chem. 256, 3580-3592) of 27 and 32.5 kilodaltons have been isolated from dissociated Anabaena variabilis phycobilisomes. In 0.05 M phosphate at pH 7.0, these "trimeric" complexes have the molar composition (alpha beta)3 . 27,000 and (alpha beta)3 . 32,500, where alpha and beta are the subunits of phycocyanin and 27,000 and 32,500 denote single copies of the linker polypeptides. The (alpha beta)3 . 27,000 and (alpha beta)3 . 32,500 complexes have lambda max at 638 and 629 nm and fluorescence emission maxima at 651 and 646 nm, respectively. In 0.6 M phosphate at pH 8.0, the (alpha beta)3 . 27,000 complex forms an (alpha beta)6 . 27,000 disc-shaped aggregate as seen in the electron microscope, whereas the (alpha beta)3 . 32,500 complex forms discs, (alpha beta)6 . 32,500, and stacked disc rods of varying lengths. The former material, containing the 27,000 polypeptide, when mixed with the (alpha beta)6 . 32,500 discs, limits their assembly into rods. The spectroscopic properties of the discs and rods assembled in vitro indicate that energy transfer in phycobilisome rod substructures proceeds from (alpha beta)6 . 32,500 discs to the (alpha beta)6 . 27,000 disc proximal to the core and thence to the core.
Highlights
From the $Departmentsof Microbiology a n d Immunology a n d !Molecular Biology, University of California, Berkeley, California 94720
In 0.6 M phosphate at pH 8.0, the (a#?)S 27,000 complex formsan (a/3)6 27,000 disc-shaped bilisomes and those of mutants which form incomplete structures, we have established that an6-27K1 disc occupies the position in the rod proximal to the core, whereas the6-30K and (~$)~-33Kdiscs form the rest of the rod substructure [8, 9]
Electron microscopic study of in vitro rod assembly indicates that trimers ( ( Y P ) ~ -aXre intermediates in rod assembly [9]
Summary
27K, 30K, 32.5K, and 33K, designations used to specify polypeptides of 27,000,30,000,32,500,and 33,000 daltons, respectively; SDS, sodium dodecyl sulfate; NaK-phosphate, NaH2P04 titratedwith KzHP04 to a given pH. Protein distribution in the gradients acrylamide gel electrophoresis. The upper band contained the phy- was determined from the absorbance a t 280 nm and SDS-polyacrvlcocyanin-27K pol.ypeptide complex and the lower the phycocyanin- amide gel electrophoresis of every fraction. Two-dimensional gel electrophoresis were prepared in 0.05 M K-phosphate, pH 7.0 These mixtures were was performed by the method of O'Farrell [18].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
