ジャーナル: Nat Microbiol / 年: 2017 タイトル: Structure of the mycobacterial ESX-5 type VII secretion system membrane complex by single-particle analysis. 著者: Katherine S H Beckham / Luciano Ciccarelli / Catalin M Bunduc / Haydyn D T Mertens / Roy Ummels / Wolfgang Lugmayr / Julia Mayr / Mandy Rettel / Mikhail M Savitski / Dmitri I Svergun / ...著者: Katherine S H Beckham / Luciano Ciccarelli / Catalin M Bunduc / Haydyn D T Mertens / Roy Ummels / Wolfgang Lugmayr / Julia Mayr / Mandy Rettel / Mikhail M Savitski / Dmitri I Svergun / Wilbert Bitter / Matthias Wilmanns / Thomas C Marlovits / Annabel H A Parret / Edith N G Houben / 要旨: Mycobacteria are characterized by their impermeable outer membrane, which is rich in mycolic acids. To transport substrates across this complex cell envelope, mycobacteria rely on type VII (also ...Mycobacteria are characterized by their impermeable outer membrane, which is rich in mycolic acids. To transport substrates across this complex cell envelope, mycobacteria rely on type VII (also known as ESX) secretion systems. In Mycobacterium tuberculosis, these ESX systems are essential for growth and full virulence and therefore represent an attractive target for anti-tuberculosis drugs. However, the molecular details underlying type VII secretion are largely unknown, due to a lack of structural information. Here, we report the molecular architecture of the ESX-5 membrane complex from Mycobacterium xenopi determined at 13 Å resolution by electron microscopy. The four core proteins of the ESX-5 complex (EccB, EccC, EccD and EccE) assemble with equimolar stoichiometry into an oligomeric assembly that displays six-fold symmetry. This membrane-associated complex seems to be embedded exclusively in the inner membrane, which indicates that additional components are required to translocate substrates across the mycobacterial outer membrane. Furthermore, the extended cytosolic domains of the EccC ATPase, which interact with secretion effectors, are highly flexible, suggesting an as yet unseen mode of substrate interaction. Comparison of our results with known structures of other bacterial secretion systems demonstrates that the architecture of type VII secretion system is fundamentally different, suggesting an alternative secretion mechanism.
生物種: Mycobacterium smegmatis str. MC2 155 (バクテリア) 組換プラスミド: pMV
分子量
理論値: 1.8 MDa
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実験情報
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構造解析
手法
ネガティブ染色法
解析
単粒子再構成法
試料の集合状態
particle
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試料調製
濃度
0.1 mg/mL
緩衝液
pH: 8 / 詳細: 20 mM Tris pH 8, 100 mM NaCl, 5 % (v/v) glycerol
染色
タイプ: NEGATIVE / 材質: Uranyl Acetate 詳細: A drop of 2% (w/v) uranyl acetate was added to a carbon-coated grid with absorbed protein and blotted after 30 s.