Probing the Dual Role of Ca<sup>2+</sup> in the <i>Allochromatium tepidum</i> LH1–RC Complex by Constructing and Analyzing Ca<sup>2+</sup>-Bound and Ca<sup>2+</sup>-Free LH1 Complexes
The genome of the mildly thermophilic hot spring purple sulfur bacterium, <i>Allochromatium</i> (<i>Alc</i>.) <i>tepidum</i>, contains a multigene <i>pufBA</i> family that encodes a series of α- and β-polypeptides, collectively forming a heterogeneous...
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2025-01-01
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| author | Mei-Juan Zou Shuai Sun Guang-Lei Wang Yi-Hao Yan Wei Ji Zheng-Yu Wang-Otomo Michael T. Madigan Long-Jiang Yu |
| author_facet | Mei-Juan Zou Shuai Sun Guang-Lei Wang Yi-Hao Yan Wei Ji Zheng-Yu Wang-Otomo Michael T. Madigan Long-Jiang Yu |
| author_sort | Mei-Juan Zou |
| collection | DOAJ |
| description | The genome of the mildly thermophilic hot spring purple sulfur bacterium, <i>Allochromatium</i> (<i>Alc</i>.) <i>tepidum</i>, contains a multigene <i>pufBA</i> family that encodes a series of α- and β-polypeptides, collectively forming a heterogeneous light-harvesting 1 (LH1) complex. The <i>Alc. tepidum</i> LH1, therefore, offers a unique model for studying an intermediate phenotype between phototrophic thermophilic and mesophilic bacteria, particularly regarding their LH1 <i>Qy</i> transition and moderately enhanced thermal stability. Of the 16 α-polypeptides in the <i>Alc. tepidum</i> LH1, six α1 bind Ca<sup>2+</sup> to connect with β1- or β3-polypeptides in specific Ca<sup>2+</sup>-binding sites. Here, we use the purple bacterium <i>Rhodospirillum rubrum</i> strain H2 as a host to express Ca<sup>2+</sup>-bound and Ca<sup>2+</sup>-free <i>Alc. tepidum</i> LH1-only complexes composed of α- and β-polypeptides that either contain or lack the calcium-binding motif WxxDxI; purified preparations of each complex were then used to test how Ca<sup>2+</sup> affects their thermostability and spectral features. The cryo-EM structures of both complexes were closed circular rings consisting of 14 αβ-polypeptides. The <i>Q<sub>y</sub></i> absorption maximum of Ca<sup>2+</sup>-bound LH1 (α1/β1 and α1/β3) was at 894 nm, while that of Ca<sup>2+</sup>-free (α2/β1) was at 888 nm, indicating that Ca<sup>2+</sup> imparts a <i>Q<sub>y</sub></i> transition of 6 nm. Crucially for the ecological success of <i>Alc. tepidum</i>, Ca<sup>2+</sup>-bound LH1 complexes were more thermostable than Ca<sup>2+</sup>-free complexes, indicating that calcium plays at least two major roles in photosynthesis by <i>Alc. tepidum</i>—improving photocomplex stability and modifying its spectrum. |
| format | Article |
| id | doaj-art-9312446568004259b1f5f6fe8f3035ba |
| institution | Kabale University |
| issn | 2218-273X |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-9312446568004259b1f5f6fe8f3035ba2025-01-24T13:25:17ZengMDPI AGBiomolecules2218-273X2025-01-0115112410.3390/biom15010124Probing the Dual Role of Ca<sup>2+</sup> in the <i>Allochromatium tepidum</i> LH1–RC Complex by Constructing and Analyzing Ca<sup>2+</sup>-Bound and Ca<sup>2+</sup>-Free LH1 ComplexesMei-Juan Zou0Shuai Sun1Guang-Lei Wang2Yi-Hao Yan3Wei Ji4Zheng-Yu Wang-Otomo5Michael T. Madigan6Long-Jiang Yu7Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, ChinaPhotosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, ChinaPhotosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, ChinaPhotosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, ChinaSchool of Life Science and Technology, Changchun University of Science and Technology, Changchun 130022, ChinaFaculty of Science, Ibaraki University, Mito 310-8512, JapanDepartment of Microbiology, School of Biological Sciences, Southern Illinois University, Carbondale, IL 62901, USAPhotosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, ChinaThe genome of the mildly thermophilic hot spring purple sulfur bacterium, <i>Allochromatium</i> (<i>Alc</i>.) <i>tepidum</i>, contains a multigene <i>pufBA</i> family that encodes a series of α- and β-polypeptides, collectively forming a heterogeneous light-harvesting 1 (LH1) complex. The <i>Alc. tepidum</i> LH1, therefore, offers a unique model for studying an intermediate phenotype between phototrophic thermophilic and mesophilic bacteria, particularly regarding their LH1 <i>Qy</i> transition and moderately enhanced thermal stability. Of the 16 α-polypeptides in the <i>Alc. tepidum</i> LH1, six α1 bind Ca<sup>2+</sup> to connect with β1- or β3-polypeptides in specific Ca<sup>2+</sup>-binding sites. Here, we use the purple bacterium <i>Rhodospirillum rubrum</i> strain H2 as a host to express Ca<sup>2+</sup>-bound and Ca<sup>2+</sup>-free <i>Alc. tepidum</i> LH1-only complexes composed of α- and β-polypeptides that either contain or lack the calcium-binding motif WxxDxI; purified preparations of each complex were then used to test how Ca<sup>2+</sup> affects their thermostability and spectral features. The cryo-EM structures of both complexes were closed circular rings consisting of 14 αβ-polypeptides. The <i>Q<sub>y</sub></i> absorption maximum of Ca<sup>2+</sup>-bound LH1 (α1/β1 and α1/β3) was at 894 nm, while that of Ca<sup>2+</sup>-free (α2/β1) was at 888 nm, indicating that Ca<sup>2+</sup> imparts a <i>Q<sub>y</sub></i> transition of 6 nm. Crucially for the ecological success of <i>Alc. tepidum</i>, Ca<sup>2+</sup>-bound LH1 complexes were more thermostable than Ca<sup>2+</sup>-free complexes, indicating that calcium plays at least two major roles in photosynthesis by <i>Alc. tepidum</i>—improving photocomplex stability and modifying its spectrum.https://www.mdpi.com/2218-273X/15/1/124light-harvesting 1 (LH1) complexpurple bacterium<i>Q<sub>y</sub></i> absorption |
| spellingShingle | Mei-Juan Zou Shuai Sun Guang-Lei Wang Yi-Hao Yan Wei Ji Zheng-Yu Wang-Otomo Michael T. Madigan Long-Jiang Yu Probing the Dual Role of Ca<sup>2+</sup> in the <i>Allochromatium tepidum</i> LH1–RC Complex by Constructing and Analyzing Ca<sup>2+</sup>-Bound and Ca<sup>2+</sup>-Free LH1 Complexes Biomolecules light-harvesting 1 (LH1) complex purple bacterium <i>Q<sub>y</sub></i> absorption |
| title | Probing the Dual Role of Ca<sup>2+</sup> in the <i>Allochromatium tepidum</i> LH1–RC Complex by Constructing and Analyzing Ca<sup>2+</sup>-Bound and Ca<sup>2+</sup>-Free LH1 Complexes |
| title_full | Probing the Dual Role of Ca<sup>2+</sup> in the <i>Allochromatium tepidum</i> LH1–RC Complex by Constructing and Analyzing Ca<sup>2+</sup>-Bound and Ca<sup>2+</sup>-Free LH1 Complexes |
| title_fullStr | Probing the Dual Role of Ca<sup>2+</sup> in the <i>Allochromatium tepidum</i> LH1–RC Complex by Constructing and Analyzing Ca<sup>2+</sup>-Bound and Ca<sup>2+</sup>-Free LH1 Complexes |
| title_full_unstemmed | Probing the Dual Role of Ca<sup>2+</sup> in the <i>Allochromatium tepidum</i> LH1–RC Complex by Constructing and Analyzing Ca<sup>2+</sup>-Bound and Ca<sup>2+</sup>-Free LH1 Complexes |
| title_short | Probing the Dual Role of Ca<sup>2+</sup> in the <i>Allochromatium tepidum</i> LH1–RC Complex by Constructing and Analyzing Ca<sup>2+</sup>-Bound and Ca<sup>2+</sup>-Free LH1 Complexes |
| title_sort | probing the dual role of ca sup 2 sup in the i allochromatium tepidum i lh1 rc complex by constructing and analyzing ca sup 2 sup bound and ca sup 2 sup free lh1 complexes |
| topic | light-harvesting 1 (LH1) complex purple bacterium <i>Q<sub>y</sub></i> absorption |
| url | https://www.mdpi.com/2218-273X/15/1/124 |
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