Crystal structure and molecular mechanism of an E/F type bilin lyase-isomerase

Indika Kumarapperuma (1) , Kes Lynn Joseph , Cong Wang (1) , Linta Biju (1) , Irin Tom (1) , Kourtney Weaver (2) , Théophile Grébert (3) , Frédéric Partensky (4) , Wendy Schluchter (2) , Xiaojing Yang (1)

1 UIC - University of Illinois [Chicago]
2 University of New Orleans
3 ECOMAP - ECOlogy of MArine Plankton
4 SBR - Station biologique de Roscoff = Roscoff Marine Station

Chromophore attachment of the light-harvesting apparatus represents one of the most important post-translational modifications in photosynthetic cyanobacteria. Extensive pigment diversity of cyanobacteria critically depends on bilin lyases that covalently attach chemically distinct chromophores to phycobiliproteins. However, how bilin lyases catalyze bilin ligation reactions and how some lyases acquire additional isomerase abilities remain elusive at the molecular level. Here, we report the crystal structure of a representative bilin lyase-isomerase MpeQ. This structure has revealed a “question-mark” protein architecture that unambiguously establishes the active site conserved among the E/F-type bilin lyases. Based on structural, mutational, and modeling data, we demonstrate that stereoselectivity of the active site plays a critical role in conferring the isomerase activity of MpeQ. We further advance a tyrosine-mediated reaction scheme unifying different types of bilin lyases. These results suggest that lyases and isomerase actions of bilin lyases arise from two coupled molecular events of distinct origin

Mots clés: Bilin lyase; crystal structure; isomerase; phycobiliprotein biogenesis; photosynthesis; stereoselectivity

Domaines: Biologie structurale [q-bio.BM]

Indika Kumarapperuma, Kes Lynn Joseph, Cong Wang, Linta Biju, Irin Tom, et al.. Crystal structure and molecular mechanism of an E/F type bilin lyase-isomerase. Structure, 2022, 30 (4), pp.564-574.E3. ⟨10.1016/j.str.2022.01.007⟩. ⟨hal-03631913⟩