NblA is essential for phycobilisome degradation in Anabaena sp. strain PCC 7120 but not for development of functional heterocysts.

Phycobilisomes (PBS) are the major light-harvesting complexes of cyanobacteria. These usually blue-coloured multiprotein assemblies are rapidly degraded when the organisms are starved for combined nitrogen. This proteolytic process causes a colour change of the cyanobacterial cells from blue-green to yellow-green ('bleaching').