EMD-32588
The Cryo-EM structure of siphonaxanthin chlorophyll a/b type light-harvesting complex II
EMD-32588
Single-particle2.8 Å
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Map released: 23/11/2022
Last modified: 26/06/2024
Sample Organism:
Codium fragile
Sample: siphonaxanthin chlorophyll a/b-type light-harvesting complex II
Fitted models: 7wlm (Avg. Q-score: 0.649)
Deposition Authors: Seki S
,
Nakaniwa T,
Castro-Hartmann P,
Sader K,
Kawamoto A
,
Tanaka H,
Qian P,
Kurisu G
,
Fujii R
Sample: siphonaxanthin chlorophyll a/b-type light-harvesting complex II
Fitted models: 7wlm (Avg. Q-score: 0.649)
Deposition Authors: Seki S
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Structural insights into blue-green light utilization by marine green algal light harvesting complex II at 2.78 angstrom.
Seki S
,
Nakaniwa T,
Castro-Hartmann P,
Sader K,
Kawamoto A
,
Tanaka H,
Qian P,
Kurisu G
,
Fujii R
(2022) Bba Adv , 2 , 100064 - 100064
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(2022) Bba Adv , 2 , 100064 - 100064
Abstract:
Light-harvesting complex II (LHCII) present in plants and green algae absorbs solar energy to promote photochemical reactions. A marine green macroalga, Codium fragile, exhibits the unique characteristic of absorbing blue-green light from the sun during photochemical reactions while being underwater owing to the presence of pigment-altered LHCII called siphonaxanthin-chlorophyll a/b-binding protein (SCP). In this study, we determined the structure of SCP at a resolution of 2.78 Å using cryogenic electron microscopy. SCP has a trimeric structure, wherein each monomer containing two lutein and two chlorophyll a molecules in the plant-type LHCII are replaced by siphonaxanthin and its ester and two chlorophyll b molecules, respectively. Siphonaxanthin occupies the binding site in SCP having a polarity in the trimeric inner core, and exhibits a distorted conjugated chain comprising a carbonyl group hydrogen bonded to a cysteine residue of apoprotein. These features suggest that the siphonaxanthin molecule is responsible for the characteristic green absorption of SCP. The replaced chlorophyll b molecules extend the region of the stromal side chlorophyll b cluster, spanning two adjacent monomers.
Light-harvesting complex II (LHCII) present in plants and green algae absorbs solar energy to promote photochemical reactions. A marine green macroalga, Codium fragile, exhibits the unique characteristic of absorbing blue-green light from the sun during photochemical reactions while being underwater owing to the presence of pigment-altered LHCII called siphonaxanthin-chlorophyll a/b-binding protein (SCP). In this study, we determined the structure of SCP at a resolution of 2.78 Å using cryogenic electron microscopy. SCP has a trimeric structure, wherein each monomer containing two lutein and two chlorophyll a molecules in the plant-type LHCII are replaced by siphonaxanthin and its ester and two chlorophyll b molecules, respectively. Siphonaxanthin occupies the binding site in SCP having a polarity in the trimeric inner core, and exhibits a distorted conjugated chain comprising a carbonyl group hydrogen bonded to a cysteine residue of apoprotein. These features suggest that the siphonaxanthin molecule is responsible for the characteristic green absorption of SCP. The replaced chlorophyll b molecules extend the region of the stromal side chlorophyll b cluster, spanning two adjacent monomers.