Stabilization of the oxygen-evolving complex of photosystem II by bicarbonate and glycinebetaine in thylakoid and subthylakoid preparations

Functional Plant Biology : FPB
V V KlimovN Murata

Abstract

The protective effect of 1 M glycinebetaine on thermal inactivation of photosynthetic oxygen evolution in isolated photosystem II membrane fragments from spinach is observed in CO2-free medium in both the presence and absence of added 2 mM bicarbonate. Conversely, the protective effect of 2 mM bicarbonate against thermoinactivation is seen in the absence as well as in the presence of 1 M glycinebetaine. The stabilizing effect of bicarbonate is also observed in thylakoid membranes from Synechococcus sp. PCC 7002 treated with 0.1% Triton X-100, and in unbroken spinach thylakoids. It is shown for the first time that bicarbonate protects the water-oxidizing complex against inactivation induced by pre-incubation of photosystem II membrane fragments (25°C) and thylakoids (40°C) at low pH (5.0-5.5) in non-bicarbonate-depleted medium. We conclude that the protective effects of glycinebetaine and bicarbonate are of a different nature; glycinebetaine acts as a non-specific, compatible, zwitterionic osmolyte while bicarbonate is considered an essential constituent of the water-oxidizing complex of photosystem II, important for its functioning and stabilization.

Citations

Apr 14, 2006·Proteomics·Hossein AskariGhasem Hosseini Salekdeh
Feb 6, 2017·Photosynthesis Research· GovindjeeLars Olof Björn
Apr 24, 2012·Biochimica Et Biophysica Acta·Dmitriy Shevela Govindjee

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