A thermoluminescence study of the effects of nitrite on photosystem II in spinach thylakoids.
The site of action of nitrite on PS II was investigated by measuring the TL profile of nitrite-treated spinach thylakoid membranes. Three bands were observed in control, which were identified as the Q band (7 degrees C), the B band (24 degrees C) and the C band (57 degrees C). In the presence of 20 mmol/L nitrite, the intensity of the Q band decreased, the B band upshifted to 46 degrees C but the C band disappeared. The suppression of the Q band and the upshift of the B band suggested that nitrite caused inhibition at the water oxidizing complex. The effects of nitrite also remained the same in the presence of chloride. In case of ion-sufficient thylakoid membranes, nitrite decreased the Q band peak intensity and caused an upshift in the B band peak temperature. Nitrite showed similar effects in the presence of DCMU. This suggested that the site of action of nitrite is not at the acceptor side but at the donor side of PS II. The inhibition shown by nitrite has been found to be specific for nitrite anion. No other anions such as formate, fluoride or nitrate, were effective.
Sahay
Archna
A
School of Life Sciences, Devi Ahilya University, Vigyan Bhavan, Khandwa Road, Indore 452001, M.P., India.
Jajoo
Anjana
A
Bharti
Sudhakar
S
D004791:Enzyme Inhibitors / Q000494:pharmacology*; D049449:Luminescence; D009573:Nitrites / Q000494:pharmacology*; D045332:Photosystem II Protein Complex / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018724:Spinacia oleracea; D013696:Temperature; D020524:Thylakoids / Q000187:drug effects* / Q000378:metabolism
D004791:Enzyme Inhibitors; D009573:Nitrites; D045332:Photosystem II Protein Complex