Figure 4
Working model of scytonemin biosynthesis based on genomic analyses. (A) UVA is absorbed and activates the proposed gene cluster to produce the corresponding protein products localized according to putative protein domains, see text for details. (B) UVA is blocked by scytonemin accumulated in the cyanobacterial sheath, which ultimately deactivates the transcription of the gene cluster and eliminates the need for the putative protein products.