Journal Article

Highly Purified Thermo-Stable Oxygen-Evolving Photosystem II Core Complex from the Thermophilic Cyanobacterium <i>Synechococcus elongatus</i> Having His-Tagged CP43

Miwa Sugiura and Yorinao Inoue

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 12, pages 1219-1231
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029510
Highly Purified Thermo-Stable Oxygen-Evolving Photosystem II Core Complex from the Thermophilic Cyanobacterium Synechococcus elongatus Having His-Tagged CP43

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The carboxyl terminus of the CP43 subunit of photosystem II (PSII) in the thermophilic cyanobacterium, Synechococcus elongatus, was genetically tagged with six consecutive histidine residues to create a metal binding site on the PSII supramolecular complex. The histidine-tagging enabled rapid isolation of an intact cyanobacterial PSII core complex from dodecyl maltoside-solubilized thylakoids by a simple one-step Ni2+-affinity column chromatography. The isolated core complex was in a dimeric form with a molecular mass of about 580 kDa, consisting of five major intrinsic membrane proteins (CP47, CP43, D1, D2 and cytochrome b-559), three extrinsic proteins (33 kDa, 12 kDa, and cytochrome c-550), and a few low molecular mass membrane proteins, and evolved oxygen at a rate as high as 3,400 μmol (mg Chl)−1 h−1 at 45°C with ferricyanide as an electron acceptor. The core complex emitted thermoluminescence B2−, B1− and Q-bands arising from S2QB, S3QB and S2QB charge recombinations at respective emission temperatures of 45, 38 and 20°C, all of which were higher by about 15°C as compared with those in mesophilic spinach BBY membranes. These results indicated that the isolated core complex well retained the intact properties of thermoluminescence of thermophilic cyanobacterial cells, the deeper stabilization of PSII charge pairs. The isolated complex was extremely stable in terms of both protein composition and function, exhibiting no release of extrinsic proteins, no proteolytic degradation in any of its subunits, accompanied by only a slight (less than 10%) loss in oxygen evolution, after dark-incubation at 20°C for 8 d. These properties of the thermophilic PSII core complex are highly useful for various types of studies on PSII.

Keywords: CP43; His-tag; Oxygen evolution; PSII core complex; Synechococcus elongatus; Thermostability

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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