Consensus model of a cyanobacterial light-dependent protochlorophyllide oxidoreductase in its pigment-free apo-form and photoactive ternary complex

Abstract

Photosynthetic organisms employ two different enzymes for the reduction of the C17 = C18 double bond of protochlorophyllide (Pchlide), yielding the chlorophyll precursor chlorophyllide. First, a nitrogenase-like, light-independent (dark-operative) Pchlide oxidoreductase and secondly, a light-dependent Pchlide oxidoreductase (LPOR). For the latter enzyme, despite decades of research, no structural information is available. Here, we use protein structure modelling, molecular dynamics (MD) simulations combined with multi-wavelength analytical ultracentrifugation (MWA-AUC) and small angle X-ray scattering (SAXS) experiments to derive a consensus model of the LPOR apoprotein and the substrate/cofactor/LPOR ternary complex. MWA-AUC and SAXS experiments independently demonstrate that the apoprotein is monomeric, while ternary complex formation induces dimerization. SAXS-guided modelling studies provide a full-length model of the apoprotein and suggest a tentative mode of dimerization for the LPOR ternary complex, supported by published cross-link constraints. Our study provides a first impression of the LPOR structural organization.

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Citation
Schneidewind, J., Krause, F., Bocola, M., Stadler, A. M., Davari, M. D., Schwaneberg, U., et al. (2019). Consensus model of a cyanobacterial light-dependent protochlorophyllide oxidoreductase in its pigment-free apo-form and photoactive ternary complex (London : Springer Nature). London : Springer Nature. https://doi.org//10.1038/s42003-019-0590-4
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CC BY 4.0 Unported