Manganese stabilizing protein of photosystem II is a thermostable, natively unfolded polypeptide

The thermostability of the manganese stabilizing protein (MSP) of photosystem II was investigated by biochemical and spectroscopic methods. Samples of both native and recombinant spinach manganese stabilizing protein incubated at 90 deg C and cooled to 25 deg C were able to rebind to, and to reactivate, the O2-evolution activity of photosystem II membranes from which the native protein had been removed. Findings showed that MSP has the identifying features of a natively unfolded protein.