ジャーナル: Proc Natl Acad Sci U S A / 年: 2013 タイトル: Structural basis for the stabilization of the complement alternative pathway C3 convertase by properdin. 著者: Martín Alcorlo / Agustín Tortajada / Santiago Rodríguez de Córdoba / Oscar Llorca / 要旨: Complement is an essential component of innate immunity. Its activation results in the assembly of unstable protease complexes, denominated C3/C5 convertases, leading to inflammation and lysis. ...Complement is an essential component of innate immunity. Its activation results in the assembly of unstable protease complexes, denominated C3/C5 convertases, leading to inflammation and lysis. Regulatory proteins inactivate C3/C5 convertases on host surfaces to avoid collateral tissue damage. On pathogen surfaces, properdin stabilizes C3/C5 convertases to efficiently fight infection. How properdin performs this function is, however, unclear. Using electron microscopy we show that the N- and C-terminal ends of adjacent monomers in properdin oligomers conform a curly vertex that holds together the AP convertase, interacting with both the C345C and vWA domains of C3b and Bb, respectively. Properdin also promotes a large displacement of the TED (thioester-containing domain) and CUB (complement protein subcomponents C1r/C1s, urchin embryonic growth factor and bone morphogenetic protein 1) domains of C3b, which likely impairs C3-convertase inactivation by regulatory proteins. The combined effect of molecular cross-linking and structural reorganization increases stability of the C3 convertase and facilitates recruitment of fluid-phase C3 convertase to the cell surfaces. Our model explains how properdin mediates the assembly of stabilized C3/C5-convertase clusters, which helps to localize complement amplification to pathogen surfaces.
名称: Human Properdin purified from plasma / タイプ: sample / ID: 1000 詳細: The structure corresponds to a head-to-tail connection between two Properdin monomers (from a tetrameric species) 集合状態: dimer / Number unique components: 1
The particles were manually selected using Boxer (EMAN1). Images were classified and averaged using maximum-likelihood multi-reference methods as implemented in XMIPP. Ab initio templates for angular refinement were obtained using the command e2initial model in EMAN2. 3D reconstructions were obtained using angular refinement using EMAN.
CTF補正
詳細: Each CCD Frame, estimated with CTFFIND and corrected using BSOFT