TY - JOUR
T1 - An integrated approach towards extracting structural characteristics of chlorosomes from a bchQ mutant of Chlorobaculum tepidum
AU - Dsouza, Lolita
AU - Li, Xinmeng
AU - Erić, Vesna
AU - Huijser, Annemarie
AU - Jansen, Thomas L.C.
AU - Holzwarth, Alfred R.
AU - Buda, Francesco
AU - Bryant, Donald A.
AU - Bahri, Salima
AU - Gupta, Karthick Babu Sai Sankar
AU - Sevink, G. J.Agur
AU - de Groot, Huub J.M.
N1 - Publisher Copyright:
© 2024 The Royal Society of Chemistry.
PY - 2024
Y1 - 2024
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85189015408&partnerID=8YFLogxK
U2 - 10.1039/d4cp00221k
DO - 10.1039/d4cp00221k
M3 - Article
AN - SCOPUS:85189015408
SN - 1463-9076
VL - 26
SP - 15856
EP - 15867
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 22
ER -