P. Maenpaa et al., SITE-SPECIFIC MUTATIONS IN THE D1-POLYPEPTIDE AFFECT THE SUSCEPTIBILITY OF SYNECHOCYSTIS-6803 CELLS TO PHOTOINHIBITION, Plant molecular biology, 22(1), 1993, pp. 1-12
Photoinhibition of photosystem II in the cyanobacterium Synechocystis
6803 was followed after site-specific mutagenesis of the DI polypeptid
e. Mutations were created in the stromal/cytosolic loop connecting hel
ices D and E. Two mutations E243K and CA1, a deletion of the three glu
tamates 242-244 and a substitution Q241H, were made in the putative cl
eavage area of the Dl polypeptide. A third mutation E229D was made in
the PEST-like sequence. Mutants and control cells were illuminated and
F(V)/F(M) was recorded. Compared to the control, the mutants were les
s photoinhibited. Fluorescence relaxation after a single flash was del
ayed in CA1. Restoration of F(V)/F(M) after photoinhibition in the mut
ants was totally dependent on protein synthesis while control cells we
re able to recover partially also when protein synthesis was inhibited
. In addition, the protein synthesis-dependent recovery of CA1 was slo
wed down. Our results indicate a correlation between the mutated amino
acids and photoinhibition of photosystem II.