| | 1 | Author
| V. A. Boichenko, V. V. Klimovb, S. R. Mayes3, J. Barber1, T. Echnology, M. Edicine, London Sw, A. Y., U. K. | Requires cookie* | | | Title
| Characterization of the Light-Induced Oxygen Gas Exchange from the IC 2 Deletion Mutant of Synechocystis PCC 6803 Lacking the Photosystem II 33 kDa Extrinsic Protein  | | | | Abstract
| The absence o f the extrinsic M n-stabilizing 33 kD a protein in the IC 2 mutant o f Synecho cystis PCC 6803 disturbs the redox cycling o f the water splitting system and retards the formation o f its higher S-states (I. Vass, K.. We have performed analyses o f the flash-induced oxygen exchange in the mutated cyanobacterium to clarify further the role o f the 33 kD a protein. Under aerobic conditions, both the wild type and IC2 mutant show a relative ly slow signal o f oxygen rise on the first flash which is increased about twice by the addition o f 10 (aM D C M U and significantly diminished by lowering the oxygen concentration in the medi um. According to action spectra measurements, this m ode o f apparent oxygen release is me diated by PS I and can be attributed to a light induced inhibition o f respiratory activity. In contrast to the wild type, having the usual oxygen evolution flash pattern with a periodicity o f four, the IC2 mutant shows a binary oscillation pattern o f flash-induced respiratory oxygen exchange at a flash frequency 10 Hz, being dampened with D C M U or by a lower flash fre quency (< 1 Hz). Oxygen evolution due to water splitting is clearly seen in the IC2 mutant when background far-red illumination is applied to saturate the signal due to respiratory inhi bition, but a quadruple oscillatory com ponent o f flash-induced oxygen evolution appears only in the presence o f artificial electron acceptors under partial aerobic conditions. The mutant possesses a higher PS I/PS II ratio compared to the wild type, as judged from both the flash-induced yields and quantum efficiencies o f the steady-state rates o f the oxygen exchange reac tions. Estimates o f antenna sizes indicate about a 20% decrease o f optical cross-section at 675 nm o f the PS II unit in IC 2 mutants in comparison with the wild type. It is suggested that the absence o f the 33 kDa protein leads to a m odification o f the PS II assembly and because o f the slowing down o f the S-state cycle, the rate o f cyclic electron flow around PS II is enhanced. It seems that the absence o f the 33 kD a protein in Synechocystis 6803 also disturbs energy transfer between adjacent PS II core complexes and may also alter their association with the phycobilisomes. | | | |
Reference
| Z. Naturforsch. 48c, 224—201 (1993); received December 10 1992 | | | |
Published
| 1993 | | | |
Keywords
| Photosystem II, Oxygen Evolution, 33 kD a Protein, Synechocystis, Mutants | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0224.pdf | | | | Identifier
| ZNC-1993-48c-0224 | | | | Volume
| 48 | |
| 2 | Author
| UweJ. Jürgens, Roland Benz | Requires cookie* | | | Title
| Pore-Forming Activity of Outer Membrane Extracts from the Unicellular Cyanobacterium Synechocystis sp. PCC 6714 | | | | Abstract
| Cell walls of the unicellular cyanobacterium Synechocystis sp. PCC 6714, isolated from cell homogenates, were found to be unusually resistant against extraction with various detergents, organic solvents, chaotropic agents, and proteases. The major outer membrane proteins (M r 67,000; 61,000; 94,000) were solubilized by differential SDS-extraction and purified by prepara tive SDS-PAGE. The extracted proteins, reconstituted into lipid bilayer membranes, formed two types of pores with single-channel conductances of 2.2 nS (pore diameter of 1.4 nm) and 0.3 nS (pore diameter not determined), respectively. Carotenoids and lipopolysaccharide were found to be associated with the extracted major proteins. | | | |
Reference
| Z. Naturforsch. 44c, 165—169 (1989); received October 10 1988 | | | |
Published
| 1989 | | | |
Keywords
| Carotenoid-Binding Protein, Cyanobacterium, Outer Membrane Protein, Porin, Protease-Resist ance, Synechocystis | | | |
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| default:Reihe_C/44/ZNC-1989-44c-0165.pdf | | | | Identifier
| ZNC-1989-44c-0165 | | | | Volume
| 44 | |
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