X-ray scattering and electron cryomicroscopy study on the effect of carotenoid biosynthesis to the structure of Chlorobium tepidum chlorosomes

TY - JOUR

T1 - X-ray scattering and electron cryomicroscopy study on the effect of carotenoid biosynthesis to the structure of Chlorobium tepidum chlorosomes

AU - Ikonen, T P

AU - Li, H

AU - Psencík, J

AU - Laurinmäki, P A

AU - Butcher, S J

AU - Frigaard, Niels-Ulrik

AU - Serimaa, R E

AU - Bryant, D A

AU - Tuma, R

N1 - Keywords: Bacterial Proteins; Biophysical Phenomena; Biophysics; Carotenoids; Chlorobium; Cryoelectron Microscopy; Genes, Bacterial; Light-Harvesting Protein Complexes; Mutation; X-Ray Diffraction

PY - 2007

Y1 - 2007

N2 - Chlorosomes, the main antenna complexes of green photosynthetic bacteria, were isolated from null mutants of Chlorobium tepidum, each of which lacked one enzyme involved in the biosynthesis of carotenoids. The effects of the altered carotenoid composition on the structure of the chlorosomes were studied by means of x-ray scattering and electron cryomicroscopy. The chlorosomes from each mutant strain exhibited a lamellar arrangement of the bacteriochlorophyll c aggregates, which are the major constituents of the chlorosome interior. However, the carotenoid content and composition had a pronounced effect on chlorosome biogenesis and structure. The results indicate that carotenoids with a sufficiently long conjugated system are important for the biogenesis of the chlorosome baseplate. Defects in the baseplate structure affected the shape of the chlorosomes and were correlated with differences in the arrangement of lamellae and spacing between the lamellar planes of bacteriochlorophyll aggregates. In addition, comparisons among the various mutants enabled refinement of the assignments of the x-ray scattering peaks. While the main scattering peaks come from the lamellar structure of bacteriochlorophyll c aggregates, some minor peaks may originate from the paracrystalline arrangement of CsmA in the baseplate.

AB - Chlorosomes, the main antenna complexes of green photosynthetic bacteria, were isolated from null mutants of Chlorobium tepidum, each of which lacked one enzyme involved in the biosynthesis of carotenoids. The effects of the altered carotenoid composition on the structure of the chlorosomes were studied by means of x-ray scattering and electron cryomicroscopy. The chlorosomes from each mutant strain exhibited a lamellar arrangement of the bacteriochlorophyll c aggregates, which are the major constituents of the chlorosome interior. However, the carotenoid content and composition had a pronounced effect on chlorosome biogenesis and structure. The results indicate that carotenoids with a sufficiently long conjugated system are important for the biogenesis of the chlorosome baseplate. Defects in the baseplate structure affected the shape of the chlorosomes and were correlated with differences in the arrangement of lamellae and spacing between the lamellar planes of bacteriochlorophyll aggregates. In addition, comparisons among the various mutants enabled refinement of the assignments of the x-ray scattering peaks. While the main scattering peaks come from the lamellar structure of bacteriochlorophyll c aggregates, some minor peaks may originate from the paracrystalline arrangement of CsmA in the baseplate.

U2 - 10.1529/biophysj.106.101444

DO - 10.1529/biophysj.106.101444

M3 - Journal article

C2 - 17468163

SN - 0006-3495

VL - 93

SP - 620

EP - 628

JO - Biophysical Journal

JF - Biophysical Journal

IS - 2

ER -