Bibliographic Details
| Title: |
An integrated approach towards extracting structural characteristics of chlorosomes from a bchQ mutant of Chlorobaculum tepidum. |
| Authors: |
Dsouza, Lolita, Li, Xinmeng, Erić, Vesna, Huijser, Annemarie, Jansen, Thomas L. C., Holzwarth, Alfred R., Buda, Francesco, Bryant, Donald A., Bahri, Salima, Gupta, Karthick Babu Sai Sankar, Sevink, G. J. Agur, de Groot, Huub J. M. |
| Source: |
Physical Chemistry Chemical Physics (PCCP); 6/14/2024, Vol. 26 Issue 22, p15856-15867, 12p |
| Abstract: |
Chlorosomes, the photosynthetic antenna complexes of green sulfur bacteria, are paradigms for light-harvesting elements in artificial designs, owing to their efficient energy transfer without protein participation. We combined magic angle spinning (MAS) NMR, optical spectroscopy and cryogenic electron microscopy (cryo-EM) to characterize the structure of chlorosomes from a bchQ mutant of Chlorobaculum tepidum. The chlorosomes of this mutant have a more uniform composition of bacteriochlorophyll (BChl) with a predominant homolog, [8Ethyl, 12Ethyl] BChl c, compared to the wild type (WT). Nearly complete 13C chemical shift assignments were obtained from well-resolved homonuclear 13C–13C RFDR data. For proton assignments heteronuclear 13C–1H (hCH) data sets were collected at 1.2 GHz spinning at 60 kHz. The CHHC experiments revealed intermolecular correlations between 132/31, 132/32, and 121/31, with distance constraints of less than 5 Å. These constraints indicate the syn–anti parallel stacking motif for the aggregates. Fourier transform cryo-EM data reveal an axial repeat of 1.49 nm for the helical tubular aggregates, perpendicular to the inter-tube separation of 2.1 nm. This axial repeat is different from WT and is in line with BChl syn–anti stacks running essentially parallel to the tube axis. Such a packing mode is in agreement with the signature of the Qy band in circular dichroism (CD). Combining the experimental data with computational insight suggests that the packing for the light-harvesting function is similar between WT and bchQ, while the chirality within the chlorosomes is modestly but detectably affected by the reduced compositional heterogeneity in bchQ. [ABSTRACT FROM AUTHOR] |
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