Research / Scientific departments / Structural Biology and Chemistry / Units and Groups / Structural Biology of Bacterial Secretion / People / Rémi Fronzes
CV and previous Work
Rémi Fronzes trained as a biochemist of membrane protein complexes during his PhD in Bordeaux. During his post-doc in Prof. Gabriel Waksman’s lab in London, he specialized in high-resolution cryo-electron microscopy (cryo-EM) and single particle analysis to determine the structure of large membrane protein complexes. He worked with two world-leading specialists in electron microscopy, Prof. Elena Orlova and Prof. Helen Saibil, to solve the cryo-EM structure of the bacterial type IV secretion core complex (Science, 2009). In parallel, he used X-ray crystallography to solve the structure of the outer-membrane complex of the bacterial type IV secretion system (Nature, 2009). In october 2009, he has been appointed as a research scientist at the CNRS and as a group leader at institut Pasteur.
Find a detailed CV here
Previous work
The subunit h of the mitochondrial F1F0 ATP synthase is essential for enzyme function and assembly
Abstract
Within the yeast mitochondrial ATP synthase, subunit h is a small nuclear-encoded protein belonging to the so-called "peripheral stalk" that connects the enzyme catalytic F1 component to the mitochondrial inner membrane. This study examines the role of subunit h in ATP synthase function and assembly using a regulatable, doxycycline-repressible, subunit h gene, to overcome the strong instability of the mitochondrial DNA (mtDNA) previously observed in strains lacking the native subunit h gene. Yeast cells expressing less than 3% of subunit h, but still containing intact mitochondrial genomes, grew poorly on respiratory substrates because of a major impairment of ATP synthesis originating from the ATP synthase, whereas the respiratory chain complexes were not affected. The lack of ATP synthesis in the subunit h depleted (dh) mitochondria was attributed to defects in the assembly/stability of the ATP synthase. A main feature of dh mitochondria was a very low content (< 6%) in the mitochondrially encoded Atp6p subunit, an essential component of the enzyme proton channel, that was in large part due to a slowing down in translation. Interestingly, depletion of subunit h resulted in dramatic changes in mitochondrial cristae morphology, which further supports the existence of a link between the ATP synthase and the folding/biogenesis of the inner mitochondrial membrane.
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Structure of a type IV secretion system core complex
Abstract
Type IV secretion systems (T4SSs) are important virulence factors used by Gram-negative bacterial pathogens to inject effectors into host cells or to spread plasmids harboring antibiotic resistance genes. We report the 15 angstrom resolution cryo-electron microscopy structure of the core complex of a T4SS. The core complex is composed of three proteins, each present in 14 copies and forming a approximately 1.1-megadalton two-chambered, double membrane-spanning channel. The structure is double-walled, with each component apparently spanning a large part of the channel. The complex is open on the cytoplasmic side and constricted on the extracellular side. Overall, the T4SS core complex structure is different in both architecture and composition from the other known double membrane-spanning secretion system that has been structurally characterized.
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Structure of the outer membrane complex of a type IV secretion system
Abstract
Type IV secretion systems are secretion nanomachines spanning the two membranes of Gram-negative bacteria. Three proteins, VirB7, VirB9 and VirB10, assemble into a 1.05 megadalton (MDa) core spanning the inner and outer membranes. This core consists of 14 copies of each of the proteins and forms two layers, the I and O layers, inserting in the inner and outer membrane, respectively. Here we present the crystal structure of a approximately 0.6 MDa outer-membrane complex containing the entire O layer. This structure is the largest determined for an outer-membrane channel and is unprecedented in being composed of three proteins. Unexpectedly, this structure identifies VirB10 as the outer-membrane channel with a unique hydrophobic double-helical transmembrane region. This structure establishes VirB10 as the only known protein crossing both membranes of Gram-negative bacteria. Comparison of the cryo-electron microscopy (cryo-EM) and crystallographic structures points to conformational changes regulating channel opening and closing.
To find out more, click here
Find a detailed CV here
Previous work
The subunit h of the mitochondrial F1F0 ATP synthase is essential for enzyme function and assembly
Abstract
Within the yeast mitochondrial ATP synthase, subunit h is a small nuclear-encoded protein belonging to the so-called "peripheral stalk" that connects the enzyme catalytic F1 component to the mitochondrial inner membrane. This study examines the role of subunit h in ATP synthase function and assembly using a regulatable, doxycycline-repressible, subunit h gene, to overcome the strong instability of the mitochondrial DNA (mtDNA) previously observed in strains lacking the native subunit h gene. Yeast cells expressing less than 3% of subunit h, but still containing intact mitochondrial genomes, grew poorly on respiratory substrates because of a major impairment of ATP synthesis originating from the ATP synthase, whereas the respiratory chain complexes were not affected. The lack of ATP synthesis in the subunit h depleted (dh) mitochondria was attributed to defects in the assembly/stability of the ATP synthase. A main feature of dh mitochondria was a very low content (< 6%) in the mitochondrially encoded Atp6p subunit, an essential component of the enzyme proton channel, that was in large part due to a slowing down in translation. Interestingly, depletion of subunit h resulted in dramatic changes in mitochondrial cristae morphology, which further supports the existence of a link between the ATP synthase and the folding/biogenesis of the inner mitochondrial membrane.
To find out more click here
Structure of a type IV secretion system core complex
Abstract
Type IV secretion systems (T4SSs) are important virulence factors used by Gram-negative bacterial pathogens to inject effectors into host cells or to spread plasmids harboring antibiotic resistance genes. We report the 15 angstrom resolution cryo-electron microscopy structure of the core complex of a T4SS. The core complex is composed of three proteins, each present in 14 copies and forming a approximately 1.1-megadalton two-chambered, double membrane-spanning channel. The structure is double-walled, with each component apparently spanning a large part of the channel. The complex is open on the cytoplasmic side and constricted on the extracellular side. Overall, the T4SS core complex structure is different in both architecture and composition from the other known double membrane-spanning secretion system that has been structurally characterized.
To find out more, click here
Structure of the outer membrane complex of a type IV secretion system
Abstract
Type IV secretion systems are secretion nanomachines spanning the two membranes of Gram-negative bacteria. Three proteins, VirB7, VirB9 and VirB10, assemble into a 1.05 megadalton (MDa) core spanning the inner and outer membranes. This core consists of 14 copies of each of the proteins and forms two layers, the I and O layers, inserting in the inner and outer membrane, respectively. Here we present the crystal structure of a approximately 0.6 MDa outer-membrane complex containing the entire O layer. This structure is the largest determined for an outer-membrane channel and is unprecedented in being composed of three proteins. Unexpectedly, this structure identifies VirB10 as the outer-membrane channel with a unique hydrophobic double-helical transmembrane region. This structure establishes VirB10 as the only known protein crossing both membranes of Gram-negative bacteria. Comparison of the cryo-electron microscopy (cryo-EM) and crystallographic structures points to conformational changes regulating channel opening and closing.
To find out more, click here