PHYCOBILIPROTEIN COMPONENTS AND CHARACTERISTICS OF THE PHYCOBILISOME FROM A THERMOPHILIC CYANOBACTERIUM MYXOSARCINA CONCINNA

A phycocyanin (PC) and three allophycocyanin (AP) components (designated PC, AP1, AP2, and AP3) were prepared from Myxosarcina concinna Printz phycobilisomes by the native gradient PAGE performed in a neutral buffer system combined with the ion exchange column chromatography on DEAE-DE52 cellulose. PC contained one beta subunit (beta(21.2)(PC)) and two alpha ones (alpha(18.1)(PC) and alpha(15.4)(PC)), and it carried two rod linkers (L-R(12.3) and L-R(10.7)) and one rod-core linker (L-RC(9.5)). AP1 and AP3 were characterized as peripheral core APs, whereas AP2 was an inner-core one. AP2 and AP3 were demonstrated to function as the terminal emitters. Each of the three APs contained two beta subunits (beta(17.4)(AP) and beta(15.7)(AP)), two alpha subunits (alpha(22.3)(AP) and alpha(19.5)(AP)) and an inner-core linker (L-C(11.3)). AP2 and AP3 had another subunit of the allophycocyanin B (AP-B) type (beta(15.1)(AP)) belonging to the beta subunit group, and AP1 and AP3 carried their individual specific core linkers (L-C(13.8) and L-C(8.3)), respectively. No AP component was shown to associate with the core-membrane linker L-CM. The functions of the linker polypeptides in the phycobilisome (PBS) construction are discussed.