MpeQ family


The mpeQ gene is present in the "PEII subregion" of the "phycobilisome rod gene region" of all PEII-containing marine Synechococcus strains belonging to pigment types 3c and 3dB (Grébert et al. 2021, 2022); it is found at the same position as mpeY in pigment types 3a and 3dA (Grébert et al. 2021, 2022). MpeQ is related to MpeY, MpeW and MpeZ, and more distantly related to CpeY. It was biochemically characterized as a PEB:Cys-83 alpha-PEII lyase-isomerase in the pigment 3dB Synechococcus strain A15-62 (Grébert et al. 2021). In Synechococcus pigment type 3c strains, this site constitutively binds a PUB, whereas in 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). The crystal structure of MpeQ has been described at 2.5-Å resolution and its "question mark" architecture is representative of all members of the E/F clan. (Kumarapperuma et al. 2022).


Phyre2 found the following protein fold for this family:



  • Grébert et al., 2022. Diversity and evolution of pigment types in marine Synechococcus cyanobacteria Genome Biol Evol, 14, evac035.
  • Grébert et al., 2021. Molecular bases of an alternative dual-enzyme system for light color acclimation of marine Synechococcus cyanobacteria Proc Natl Acad Sci USA, 118, e2019715118.
  • Humily et al., 2013. A gene island with two possible configurations is involved in chromatic acclimation in marine Synechococcus PLoS One, 8, e84459.
  • Kumarapperuma et al., 2022. Crystal structure and molecular mechanism of an E/F type bilin lyase-isomerase Structure, 30, 564-574.

Gene Locus tag Genbank Species Strain PBP in rods Pigment type Remark Length Last change
MpeQ family Syncc9605_0436 YP_380767.1 Synechococcus sp. CC9605 PC+PEI+PEII 3c 398 04-20-2023
MpeQ family SH8109_0069 ZP_05788234.1 Synechococcus sp. WH8109 PC+PEI+PEII 3bB 398 04-20-2023
MpeQ family SYNW2007 NP_898098.1 Synechococcus sp. WH8102 PC+PEI+PEII 3c 398 04-20-2023

Model strain Model strains, Marine strains

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