6HBB

Crystal Structure of the small subunit-like domain 1 of CcmM from Synechococcus elongatus (strain PCC 7942)

6HBB の概要

• エントリーDOI: 10.2210/pdb6hbb/pdb
• 分子名称: Carbon dioxide concentrating mechanism protein CcmM, SULFATE ION (3 entities in total)
• 機能のキーワード: alpha-beta structure, rubisco, carboxysome, protein binding
• 由来する生物種: Synechococcus elongatus (strain PCC 7942) (Anacystis nidulans R2)
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 21773.81

構造登録者

Wang, H.,Yan, X.,Aigner, H.,Bracher, A.,Nguyen, N.D.,Hee, W.Y.,Long, B.M.,Price, G.D.,Hartl, F.U.,Hayer-Hartl, M. (登録日: 2018-08-10, 公開日: 2018-12-12, 最終更新日: 2024-01-17)

主引用文献

Wang, H.,Yan, X.,Aigner, H.,Bracher, A.,Nguyen, N.D.,Hee, W.Y.,Long, B.M.,Price, G.D.,Hartl, F.U.,Hayer-Hartl, M.
Rubisco condensate formation by CcmM in beta-carboxysome biogenesis.
Nature, 566:131-135, 2019

PubMed Abstract: Cells use compartmentalization of enzymes as a strategy to regulate metabolic pathways and increase their efficiency. The α- and β-carboxysomes of cyanobacteria contain ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)-a complex of eight large (RbcL) and eight small (RbcS) subunits-and carbonic anhydrase. As HCO can diffuse through the proteinaceous carboxysome shell but CO cannot, carbonic anhydrase generates high concentrations of CO for carbon fixation by Rubisco. The shell also prevents access to reducing agents, generating an oxidizing environment. The formation of β-carboxysomes involves the aggregation of Rubisco by the protein CcmM, which exists in two forms: full-length CcmM (M58 in Synechococcus elongatus PCC7942), which contains a carbonic anhydrase-like domain followed by three Rubisco small subunit-like (SSUL) modules connected by flexible linkers; and M35, which lacks the carbonic anhydrase-like domain. It has long been speculated that the SSUL modules interact with Rubisco by replacing RbcS. Here we have reconstituted the Rubisco-CcmM complex and solved its structure. Contrary to expectation, the SSUL modules do not replace RbcS, but bind close to the equatorial region of Rubisco between RbcL dimers, linking Rubisco molecules and inducing phase separation into a liquid-like matrix. Disulfide bond formation in SSUL increases the network flexibility and is required for carboxysome function in vivo. Notably, the formation of the liquid-like condensate of Rubisco is mediated by dynamic interactions with the SSUL domains, rather than by low-complexity sequences, which typically mediate liquid-liquid phase separation in eukaryotes. Indeed, within the pyrenoids of eukaryotic algae, the functional homologues of carboxysomes, Rubisco adopts a liquid-like state by interacting with the intrinsically disordered protein EPYC1. Understanding carboxysome biogenesis will be important for efforts to engineer CO-concentrating mechanisms in plants.

PubMed: 30675061
DOI: 10.1038/s41586-019-0880-5

実験手法

X-RAY DIFFRACTION (1.2 Å)