Pascal François Egea, Ph.D.

During my post-doctoral training in the laboratory of Robert Stroud at UCSF, I studied the molecular mechanisms of protein targeting towards membranes mediated by the SRP (Signal Recognition Particle) using crystallography and solution scattering techniques. My work emphasized on the characterization (expression, reconstitution/purification and characterization) of the protein-protein and protein-RNA complexes involved in this process. I solved to 1.9-Å resolution the X-ray structure of the complex between the SRP and its receptor (Egea et al., Nature 2004) responsible for the regulated delivery of ribosomes harboring nascent polypeptidic chains destined for secretion or membrane insertion to the translocon, the integral membrane protein complex responsible for their translocation into or across membranes (Egea et al., COSB 2005). I then acquired experience in the expression, purification and crystallization of membrane proteins, focusing again on the protein translocation step. My work as a membrane protein structural biologist focused on the translocon, the protein-conducting channel responsible for the secretion across or insertion into biological membranes in all living cells. I successfully expressed the translocon from the archaeon Pyrococcus furiosus; this work implied the co-expression in E. coli of the three subunits constituting a functional translocon. Following the purification and crystallization of the archeal channel, I solved its structure to 2.9Å resolution using the multiple wavelength anomalous dispersion phasing method and starting from crystals barely diffracting to 40Å resolution and suffering from severe anisotropy of diffraction. The structural study was complemented by a functional analysis using in vivo complementation test (Egea & Stroud, PNAS 2010).

Recent and Selected Publications

Savage DF, Egea PF, Robles-Colmenares Y, O’Connell JD, 3rd, Stroud RM. Architecture and selectivity in aquaporins: 2.5Å X-ray structure of aquaporin Z. PLoS Biol. 2003;1(3):E72. PMID 14691544 PMCID: 300682.

Egea PF, Shan SO, Napetschnig J, Savage DF, Walter P, Stroud RM. Substrate twinning activates the signal recognition particle and its receptor. Nature. 2004;427(6971):215-221. PMID: 14724630.

Egea PF, Stroud RM, Walter P. Targeting proteins to membranes: structure of the signal recognition particle. Curr Opin Struct Biol. 2005;15(2):213-220. PMID: 15837181.

Egea PF, Tsuruta H, de Leon GP, Napetschnig J, Walter P, Stroud RM. Structures of the signal recognition particle receptor from the archaeon Pyrococcus furiosus: implications for the targeting step at the membrane. PLoS One. 2008;3(11):e3619. PMCID: 2572998.

Egea PF, Napetschnig J, Walter P, Stroud RM. Structures of SRP54 and SRP19, the two proteins that organize the ribonucleic core of the signal recognition particle from Pyrococcus furiosus. PLoS One. 2008;3(10):e3528. PMCID: 2568955.

Korennykh AV, Egea PF, Korostelev AA, Finer-Moore J, Zhang C, Shokat KM, et al. The unfolded protein response signals through high-order assembly of Ire1. Nature. 2009;457(7230):687-693. PMID: 19079236. PMCID: PMC2846394. Free PMC Article.

Egea PF, Stroud RM. Lateral opening of a translocon upon entry of protein protein suggests the mechanism of insertion into membranes, Proc Natl Acad Sci U S A. 2010; 107(40):17182-17187 PMID: 20855604. PMCID: PMC2951439.

 

The lateral gate of the channel of the Pfu-SecYE channel is entirely opened while its plug remains in place, still occluding the central conduit. (A) Surface representations of the translocons from Mja, Tth, and Pfu showing the different states of the lateral gate. The SecY, SecE, and Secβ subunits are colored in green, red, and cyan, respectively. The αC-helix contributed by a symmetry-related SecYE complex is shown as a yellow surface to emphasize its insertion into the cytoplasmic vestibule. In Tth and Pfu, the so-called hydrophobic crack observed in Tth-SecYE (8) and the complete lateral gate opening in Pfu-SecYE are shown as a dotted white line. The plug helix is colored in pink and can only be clearly seen in the Pfu structure because of the extensive lateral gate. (B) Schematics of the three conformations shown in A.