ジャーナル: Mol Plant / 年: 2024 タイトル: Unique biogenesis and kinetics of hornwort Rubiscos revealed by synthetic biology systems. 著者: Zhen Guo Oh / Tanner Ashton Robison / Dan Hong Loh / Warren Shou Leong Ang / Jediael Zheng Ying Ng / Fay-Wei Li / Laura Helen Gunn / 要旨: Hornworts are the only land plants that employ a pyrenoid to optimize Rubisco's CO fixation, yet hornwort Rubisco remains poorly characterized. Here we assembled the hornwort Anthoceros agrestis ...Hornworts are the only land plants that employ a pyrenoid to optimize Rubisco's CO fixation, yet hornwort Rubisco remains poorly characterized. Here we assembled the hornwort Anthoceros agrestis Rubisco (AaRubisco) using the Arabidopsis thaliana SynBio expression system and observed the formation of stalled intermediates, prompting us to develop a new SynBio system with A. agrestis cognate chaperones. We successfully assembled AaRubisco and Rubisco from three other hornwort species. Unlike A. thaliana Rubisco, AaRubisco assembly is not dependent on RbcX or Raf2. Kinetic characterization reveals that hornwort Rubiscos exhibit a range of catalytic rates (3-10 s), but with similar affinity (∼30 μM) and specificity (∼70) for CO. These results suggest that hornwort Rubiscos do not comply with the long-held canonical catalytic trade-off observed in other land plants, providing experimental support that Rubisco kinetics may be phylogenetically constrained. Unexpectedly, we observed a 50% increase in AaRubisco catalytic rates when RbcX was removed from our SynBio system, without any reduction in specificity. Structural biology, biochemistry, and proteomic analysis suggest that subtle differences in Rubisco large-subunit interactions, when RbcX is absent during biogenesis, increases the accessibility of active sites and catalytic turnover rate. Collectively, this study uncovered a previously unknown Rubisco kinetic parameter space and provides a SynBio chassis to expand the survey of other Rubisco kinetics. Our discoveries will contribute to developing new approaches for engineering Rubisco with superior kinetics.
A: RuBisCO large subunit B: RuBisCO large subunit C: RuBisCO large subunit D: RuBisCO large subunit E: RuBisCO large subunit F: RuBisCO large subunit G: RuBisCO large subunit H: RuBisCO large subunit I: RuBisCO small subunit J: RuBisCO small subunit K: RuBisCO small subunit L: RuBisCO small subunit M: RuBisCO small subunit N: RuBisCO small subunit O: RuBisCO small subunit P: RuBisCO small subunit ヘテロ分子
モード: BRIGHT FIELD / 倍率(公称値): 63000 X / 最大 デフォーカス(公称値): 2500 nm / 最小 デフォーカス(公称値): 500 nm / アライメント法: BASIC
試料ホルダ
凍結剤: NITROGEN
撮影
平均露光時間: 4.8 sec. / 電子線照射量: 65 e/Å2 / フィルム・検出器のモデル: GATAN K3 (6k x 4k) / 撮影したグリッド数: 1 詳細: Images were collected over 50 movie frames in super resolution mode
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解析
EMソフトウェア
ID
名称
バージョン
カテゴリ
2
PHENIX
1.20.1_4487:
モデル精密化
3
EPU
画像取得
13
cryoSPARC
3次元再構成
CTF補正
タイプ: PHASE FLIPPING AND AMPLITUDE CORRECTION
粒子像の選択
選択した粒子像数: 761107
対称性
点対称性: D4 (2回x4回 2面回転対称)
3次元再構成
解像度: 3 Å / 解像度の算出法: FSC 0.143 CUT-OFF / 粒子像の数: 87259 / 対称性のタイプ: POINT