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Primary and Higher Order Structure of the Reaction Center from the Purple Phototrophic Bacterium Blastochloris viridis: A Test for Native Mass Spectrometry
journal contribution
posted on 2018-02-21, 00:00 authored by Yue Lu, Carrie Goodson, Robert E. Blankenship, Michael L. GrossThe reaction center
(RC) from the phototrophic bacterium Blastochloris
viridis was the first integral membrane
protein complex to have its structure determined by X-ray crystallography
and has been studied extensively since then. It is composed of four
protein subunits, H, M, L, and C, as well as cofactors, including
bacteriopheophytin (BPh), bacteriochlorophyll (BCh), menaquinone,
ubiquinone, heme, carotenoid, and Fe. In this study, we utilized mass
spectrometry-based proteomics to study this protein complex via bottom-up
sequencing, intact protein mass analysis, and native MS ligand-binding
analysis. Its primary structure shows a series of mutations, including
an unusual alteration and extension on the C-terminus of the M-subunit.
In terms of quaternary structure, proteins such as this containing
many cofactors serve to test the ability to introduce native-state
protein assemblies into the gas phase because the cofactors will not
be retained if the quaternary structure is seriously perturbed. Furthermore,
this specific RC, under native MS, exhibits a strong ability not only
to bind the special pair but also to preserve the two peripheral BCh’s.