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Ziegler, I. ; Hampp, R.

Control of 35SO42- and 35SO32- incorporation into spinach chloroplasts during photosynthetic CO2 fixation.

Planta 137, 303-307 (1977)
DOI
Open Access Green as soon as Postprint is submitted to ZB.
In addition to membrane translocation, measured in the dark, it was found that pre-illumination of the chloroplasts resulted in an enhancement of sulfate uptake by 25% and of sulfite uptake by 55% as soon as the concentration of the ion in the incubation medium exceeded 2 mmol l-1. This amount which is additionally taken up after pre-illumination is less readily exchanged for other ions. Kinetics of the uptake in relation to pre-illumination time and to light intensity closely parallel those of titration of SH-groups by 5,5′-dithiobis (2-nitrobenzoic acid). As a consequence, 10-6 mol l-1 DCMU completely inhibits the light triggered increase of uptake of both ions. Uncoupling with 10-6 mol l-1 CCCP increases the light induced 35SO3 2-binding, but decreases that of 35SO4 2-, demonstrating the need of ATP formation to initiate sulfate reduction. Rates of uptake, measured at different intensities of pre-illumination under nitrogen or in the presence of bicarbonate, suggest that the presence of a carbon skeleton increases the binding rate for both ions. With respect to 35SO4 2-, the data further indicate a rate limiting step (ATP sulfurylase or adenosine 5′-phosphosulfate sulfotransferase) which is activated by light, thus representing a control step to harmonize the rate of CO2 fixation and of sulfate incorporation. On the contrary, 35SO3 2-is directly bound in relation to the amount of SH-groups, which in turn are created by the photosynthetic electron transport, resulting in Car-S-SO3 -. Since the formation of SH-groups is maximal already at low light intensities, no effective control step for SO3 2-incorporation is indicated.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Chloroplasts ; Co2-fixation ; Sh-groups ; Sulfate Incorporation ; Sulfite Incorporation
ISSN (print) / ISBN 0032-0935
e-ISSN 1432-2048
Journal Planta
Quellenangaben Volume: 137, Issue: 3, Pages: 303-307 Article Number: , Supplement: ,
Publisher Springer
Reviewing status Peer reviewed
Institute(s) Institut für Biochemie