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Reconstitution of 3-Acetyl Chlorophyll a into Light-Harvesting Complex 2 from the Purple Photosynthetic Bacterium Phaeospirillum molischianum.


ABSTRACT: The manipulation of B800 bacteriochlorophyll (BChl) a in light-harvesting complex 2 (LH2) from the purple photosynthetic bacterium Phaeospirillum molischianum (molischianum-LH2) provides insight for understanding the energy transfer mechanism and the binding of cyclic tetrapyrroles in LH2 proteins since molischianum-LH2 is one of the two LH2 proteins whose atomic-resolution structures have been determined and is a representative of type-2 LH2 proteins. However, there is no report on the substitution of B800 BChl a in molischianum-LH2. We report the reconstitution of 3-acetyl chlorophyll (AcChl) a, which has a 17,18-dihydroporphyrin skeleton, to the B800 site in molischianum-LH2. The 3-acetyl group in AcChl a formed a hydrogen bond with ?'-Thr23 in essentially the same manner as native B800 BChl a, but this hydrogen bond was weaker than that of B800 BChl a. This change can be rationalized by invoking a small distortion in the orientation of the 3-acetyl group in the B800 cavity by dehydrogenation in the B-ring from BChl a. The energy transfer from AcChl a in the B800 site to B850 BChl a was about 5-fold slower than that from native B800 BChl a by a decrease of the spectral overlap between energy-donating AcChl a and energy-accepting B850 BChl a.

SUBMITTER: Saga Y 

PROVIDER: S-EPMC7114761 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Reconstitution of 3-Acetyl Chlorophyll <i>a</i> into Light-Harvesting Complex 2 from the Purple Photosynthetic Bacterium <i>Phaeospirillum molischianum</i>.

Saga Yoshitaka Y   Yamashita Madoka M   Imanishi Michie M   Kimura Yukihiro Y   Masaoka Yuto Y   Hidaka Tsubasa T   Nagasawa Yutaka Y  

ACS omega 20200318 12


The manipulation of B800 bacteriochlorophyll (BChl) <i>a</i> in light-harvesting complex 2 (LH2) from the purple photosynthetic bacterium <i>Phaeospirillum molischianum</i> (<i>molischianum</i>-LH2) provides insight for understanding the energy transfer mechanism and the binding of cyclic tetrapyrroles in LH2 proteins since <i>molischianum</i>-LH2 is one of the two LH2 proteins whose atomic-resolution structures have been determined and is a representative of type-2 LH2 proteins. However, there  ...[more]

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