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'33 kD a Protein' in keywords Facet   Publication Year 1993  [X]
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1Author    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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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0224.pdf 
 Identifier    ZNC-1993-48c-0224 
 Volume    48