Diversity and roles of cysteine desulfurases in photosynthetic organisms.

As sulfur is part of many essential protein cofactors such as iron-sulfur cluster, molybdenum cofactor or lipoic acid, its mobilization from cysteine represents a fundamental process. The abstraction of sulfur atom from cysteine is catalyzed by highly conserved pyridoxal 5'-phosphate-dependent enzymes called cysteine desulfurases. The desulfuration of cysteine leads to the formation of a persulfide group on a conserved catalytic cysteine and the concomitant release of alanine. Sulfur is then transferred from cysteine desulfurases to different targets. Numerous studies focused on cysteine desulfurases as sulfur-extracting enzymes for iron-sulfur cluster synthesis in mitochondria and chloroplasts but also for molybdenum cofactor sulfuration in the cytosol. Despite this, knowledge about the involvement of cysteine desulfurases in other pathways is quite rudimentary and more particularly in photosynthetic organisms. In this review, we summarize the current understanding about the different groups of cysteine desulfurases and their characteristics in terms of primary sequences, protein domain architectures and subcellular localizations. In addition, we review the roles of cysteine desulfurases in different fundamental pathways and highlight the gaps of knowledge to encourage future work on unresolved issues especially in photosynthetic organisms.