<i>In vivo</i> localization and oligomerization of PixD and PixE for controlling phototaxis in the cyanobacterium <i>Synechocystis</i> sp. PCC 6803

Phototaxis is a phenomenon where cyanobacteria move toward light source. Previous studies have shown that the blue-light-using-flavin (BLUF)-type photoreceptor PixD and response regulator-like protein PixE control phototaxis in cyanobacterium Synechocystis sp. PCC 6803. The pixD-null mutant moves away from light, whereas WT, pixE mutant, pixD double light. This indicates functions downstream of influences direction movement. However, it still unclear how signal received by transmitted to PixE, then subsequently type IV pili motor mechanism. Here, we investigated intracellular localization oligomerization elucidate mechanisms regulation. Blue-native PAGE analysis, coupled with western blotting, indicated most exist as dimer soluble fractions, localized ~250 kDa ~450 complexes membrane fractions. When blue-native was performed after illuminating fractions blue levels were reduced increased, respectively. These results suggest complex, controls activity ATPase PilB1 regulate pilus motility.