Hill reaction site in chloroplast membranes: non-participation of the quantasome particle in photoreduction |
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| Authors: | S H Howell E N Moudrianakis |
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| Affiliation: | 1. Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong, China;2. Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Hong Kong, China;3. Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, China;4. Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China;5. Division of Speech and Hearing Sciences, The University of Hong Kong, Hong Kong, China;6. Osborne College of Audiology, Salus University, Elkins Park, PA, USA;7. Department of Anatomy, The University of Hong Kong, Hong Kong, China;8. Department of Medicine, The University of Hong Kong, Hong Kong, China;1. Universidad de Navarra, Facultad de Ciencias, Departamento de Química, Laboratorio Integrado de Calidad Ambiental (LICA), Campus Universitario, Irunlarrea 1, 31008 Pamplona, Spain;2. Universidad de Navarra, Facultad de Ciencias, Departamento de Biología Ambiental, Campus Universitario, Irunlarrea 1, 31008 Pamplona, Spain;3. Universidad Autónoma de Madrid, Departmento de Ecología, Darwin 2, 28049 Madrid, Spain |
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| Abstract: | The site of the Hill reaction in spinach chloroplast membranes has been studied, primarily by electron microscopy. Evidence is presented that the membrane-bound particles, known as quantasomes, in salt-extracted preparations are not Hill reaction sites. The membrane-bound particles failed to deposit locally an electron-dense tetrazolium salt, INT, used as a Hill oxidant. Rather, entire membranes appeared to participate uniformly in INT deposition. It was found that specific INT deposition on chloroplast membranes results from photo-reduction. Competition experiments with Hill reaction substrates suggest that INT is reduced at the same site as DCPIP.EDTA extraction yielded particle-free membranes fully active in photoreduction. A non-chlorophyllous protein species is recoverable from the EDTA extracts. |
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