Fig. 5.

Hypothetical scheme invoking the involvement of nitric oxide, mycothiol and Wbl proteins in major physiological or developmental decisions. It is supposed that early actinobacteria possessed the functions coloured grey green. They made phosphoinositol-containing phospholipids and used Wbl proteins to respond to nitrosative stress (the pink arrows indicate downstream regulatory events of different Wbl states). The putative nitrobindin may have aided the denitrosylation of Wbl:NO proteins. It is further suggested that the subsequent acquisition of mycothiol biosynthetic genes and MSNO reductase greatly increased the efficiency of NO removal and Wbl regeneration.