
Full text loading...
The Structure and Function of Type III Secretion Systems, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555819286/9781555819279_Chap09-1.gif /docserver/preview/fulltext/10.1128/9781555819286/9781555819279_Chap09-2.gifAbstract:
Type III secretion systems (T3SSs) afford Gram-negative bacteria an intimate means of altering the biology of their eukaryotic hosts—the direct delivery of effector proteins from the bacterial cytoplasm to that of the eukaryote ( 1 , 2 ). T3SSs utilize a conserved set of homologous gene products to assemble the nanosyringe “injectisomes” capable of traversing the three plasma membranes, peptidoglycan layer, and extracellular space that form a barrier to the direct delivery of proteins from bacterium to host. While the injectisome is architecturally similar across disparate Gram-negative organisms, its applications are a study in diversity: T3SSs are employed by both symbionts and pathogens; they target animals, plants, and protists; and they are used to manipulate a wide array of cellular activities and pathways.
Virulence Mechanisms of Bacterial Pathogens, Fifth Edition
. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.VMBF-0004-2015Full text loading...
Virulence Mechanisms of Bacterial Pathogens, Fifth Edition
. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.VMBF-0004-2015Gross architecture of the T3SS. Cryo-EM reconstruction of the Salmonella enterica serovar Typhimurium injectisome basal body at subnanometer resolution reveals its overall architecture. (A) Surface representation of the highest resolution cryo-EM map (EMD 1875, contour level 0.0233) published by Schraidt and Marlovits ( 27 ). Dashed lines indicate the positions of bacterial membranes in vivo. Abbreviations: OR, outer ring; IR, inner ring; OM, outer membrane; IM, inner membrane. (B) An axial section through the map in (A). (C) Transverse sections through the map in (A) at the level of the neck (top) and IR1 (bottom).
Gross architecture of the T3SS. Cryo-EM reconstruction of the Salmonella enterica serovar Typhimurium injectisome basal body at subnanometer resolution reveals its overall architecture. (A) Surface representation of the highest resolution cryo-EM map (EMD 1875, contour level 0.0233) published by Schraidt and Marlovits ( 27 ). Dashed lines indicate the positions of bacterial membranes in vivo. Abbreviations: OR, outer ring; IR, inner ring; OM, outer membrane; IM, inner membrane. (B) An axial section through the map in (A). (C) Transverse sections through the map in (A) at the level of the neck (top) and IR1 (bottom).
Virulence Mechanisms of Bacterial Pathogens, Fifth Edition
. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.VMBF-0004-2015Hybrid models of basal body structure. (A) Computational modeling of the neck (SctC, PDB 3J1V), IR1 (SctD, PDB 3J1X), and IR2 (SctD, PDB 3J1W) annuli of the Salmonella enterica serovar Typhimurium basal body. No high-resolution structural information is available for the basal body above the neck. (B) In this model, complementary electrostatic surfaces support ring building, as shown for the SctD periplasmic domains. Note the modular domain architecture (enumerated 1, 2, 3) for SctDperiplasmic.
Hybrid models of basal body structure. (A) Computational modeling of the neck (SctC, PDB 3J1V), IR1 (SctD, PDB 3J1X), and IR2 (SctD, PDB 3J1W) annuli of the Salmonella enterica serovar Typhimurium basal body. No high-resolution structural information is available for the basal body above the neck. (B) In this model, complementary electrostatic surfaces support ring building, as shown for the SctD periplasmic domains. Note the modular domain architecture (enumerated 1, 2, 3) for SctDperiplasmic.
Virulence Mechanisms of Bacterial Pathogens, Fifth Edition
. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.VMBF-0004-2015Chaperone-substrate interactions. Structural distinctions between effector-chaperone and translocator-chaperone complexes. (A) The structure of the Salmonella effector SipA chaperone-binding domain (CBD, red and yellow) in complex with the class IB chaperone InvB (dark gray, light gray). PDB 2FM8 ( 47 ). The structurally conserved β-motif is highlighted in yellow. (B) The SipA β-motif is bound by a hydrophobic (gray) patch on the InvB surface (blue/gray). (C) Superposition of the CBDs from effectors from multiple species shows a common binding mode marked by the structurally conserved β-motif. The prototypical class I chaperone SicP is shown in place of the various chaperones. PDB codes: YopN, 1XKP ( 153 ); YopE, 1L2W ( 170 ); YscM2, 1TTW ( 171 ); SptP-SicP, 1JYO ( 88 ); SipA, 2FM8 ( 47 ); HopA1, 4G6T ( 93 ). (D) The Yersinia translocator YopD CBD (red) lacks secondary structure and is bound by the concave cleft of the class II chaperone SycD (gray). Protein Data bank ID number 4AM9 (PDB 4AM9) ( 172 ).
Chaperone-substrate interactions. Structural distinctions between effector-chaperone and translocator-chaperone complexes. (A) The structure of the Salmonella effector SipA chaperone-binding domain (CBD, red and yellow) in complex with the class IB chaperone InvB (dark gray, light gray). PDB 2FM8 ( 47 ). The structurally conserved β-motif is highlighted in yellow. (B) The SipA β-motif is bound by a hydrophobic (gray) patch on the InvB surface (blue/gray). (C) Superposition of the CBDs from effectors from multiple species shows a common binding mode marked by the structurally conserved β-motif. The prototypical class I chaperone SicP is shown in place of the various chaperones. PDB codes: YopN, 1XKP ( 153 ); YopE, 1L2W ( 170 ); YscM2, 1TTW ( 171 ); SptP-SicP, 1JYO ( 88 ); SipA, 2FM8 ( 47 ); HopA1, 4G6T ( 93 ). (D) The Yersinia translocator YopD CBD (red) lacks secondary structure and is bound by the concave cleft of the class II chaperone SycD (gray). Protein Data bank ID number 4AM9 (PDB 4AM9) ( 172 ).
Virulence Mechanisms of Bacterial Pathogens, Fifth Edition
. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.VMBF-0004-2015Virulence Mechanisms of Bacterial Pathogens, Fifth Edition
. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.VMBF-0004-2015A unified nomenclature for the homologous core components of the T3SS a
A unified nomenclature for the homologous core components of the T3SS a
Virulence Mechanisms of Bacterial Pathogens, Fifth Edition
. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.VMBF-0004-2015