title: Purification of a Photosystem II reaction center from a thermophilic cyanobacterium using immobilized metal affinity chromatography.
abstract: Oxygen-evolving PS II particles from the thermophilic cyanobacterium Synechococcus elongatus are partially purified by centrifugation on a sucrose gradient and are bound to a Chelating Sepharose column loaded with Cu(2+) ions. Bound particles are then transformed into PS II RC complexes by two washing steps. First, washing with a phosphate buffer (pH=6.5) containing 0.02% of SB 12 removes the rest of phycobilins and leaves pure PS II core particles on the column. Second, washing with a phosphate buffer (pH=6.2) containing 0.2 M LiClO4 and 0.05% of DM removes CP 47 and CP 43 and leaves bare PS II RC complexes on the column. These are then eluted with a phosphate buffer containing 1% of dodecylmaltoside (DM). The molar ratio of pigments in the eluate changes with the progress of elution but around the middle of the elution period a nearly stable ratio is maintained of Chl a: Pheo a: Car: Cyt b 559 equal to 2.9: 1: 0.9: 0.8. In these fractions the photochemical separation of charges could be demonstrated by accumulation of reduced pheophytin (ΔA of 430-440 nm) and by the flash induced formation of P680(+) (ΔA at 820 nm). The relatively slow relaxation kinetics of the latter signal (t1/2 ≈ 1 ms) may suggest that in a substantial fraction of the RCs QA remains bound to the complex.
authors.affiliation: Institute of Microbiology, Academy of Science of the Czech Republic, CS 37901, Trebon, Czech Republic.
authors.forename: E
authors.initials: E
authors.lastname: Setlíková
authors.forename: S
authors.initials: S
authors.lastname: Ritter
authors.forename: R
authors.initials: R
authors.lastname: Hienerwadel
authors.forename: J
authors.initials: J
authors.lastname: Kopecký
authors.forename: J
authors.initials: J
authors.lastname: Komenda
authors.forename: W
authors.initials: W
authors.lastname: Welte
authors.forename: I
authors.initials: I
authors.lastname: Setlík