MpeW family

MpeW is specific of marine Synechococcus strains belonging to pigment type 3dB, one of the two kinds of type IV chromatic acclimaters. The mpeW gene is located in the CA4-B genomic island, also comprising the two transcriptional regulator genes fciA and fciB (Sanfilippo et al. 2016). The CA4-B island is localized in the middle of the phycobilisome rod region (Humily et al. 2013, Grébert et al. 2021, 2022). MpeW has been biochemically characterized as a PEB:Cys-83 alpha-PEII lyase in Synechococcus strain A15-62 (Grébert et al. 2021). In this and other pigment type 3dB strains, this site binds a PUB in blue light and a PEB in green light, as the result of a competition between the constitutively expressed mpeQ gene and the PEB lyase gene mpeW, which is strongly activated in green light but repressed in blue light (Humily et al. 2013; Grébert et al. 2021). Given its high specificity, the mpeW gene has also been used as a biomarker to study the abundance and distribution of pigment type 3dB populations in the field (Grébert et al. 2018).