Cold-sensitive assembly of a mutant manganese-stabilizing protein caused by a Val to Ala replacement

The substitution of Val235 with Ala induces an activation energy barrier for assembly of manganese-stabilizing protein (MSP) into photosystem II (PSII). Far-UV circular dichroism spectrometry studies reveal that low temperatures destabilize the V235A mutant MSP more than the wild type protein. Temperature however, affects the secondary structure of the mutant and the wild-type protein to a small extent. The mutation appears to suppress isomerization of one or more prolyl peptide bonds necessary for assembly of MSP into PSII.