Andrea Dessen


Since July, 2012 – Researcher, Group Leader at LNBio-CNPEM

Phone: +55 19 3512.1267





Our group is interested in studying mechanisms employed by bacteria to initiate infection by tackling a number of different systems:

  •  Proteins which participate in the formation of the bacterial cell wall;
  •  The type III secretion system (T3SS) of major human pathogens, such as Pseudomonas aeruginosa and Escherichia coli.



Bacterial cell wall formation

  • Structural and functional study of PBPs from bacterial pathogens

Collaborations: A. Zapun, T. Vernet, J.P. Simorre (IBS); W. Vollmer (Newcastle Univ. UK); E. Breukink (Univ. Utrecht, Holland); S. Gobec (Univ. Ljubljana, Slovenia); T. Solmajer (Lek Pharmaceuticals, Slovenia); C. Schofield (Univ. Oxford); B. Joris (Univ. Liège); I. Boneca (Institut Pasteur)

      Bacteria carry multiple PBPs; S. pneumoniae, one of our model organisms, has six PBPs, three of which catalyze both glycosyltransfer and transpeptidation (PBPs 1a, 1b, and 2a; class A), two which catalyze uniquely the transpeptidation reaction (PBPs 2x and 2b; class B), and PBP3, a D,D-carboxypeptidase. Notably, it is precisely the transpeptidation reaction that is targeted by beta-lactams. These antibiotics, whose structure emulates that of the C-terminus of the pentapeptide, form a covalent complex within the TP domain of PBPs, blocking transpeptidation and weakening the peptidoglycan, which often leads to cell death. Gram-positive bacteria such as S. pneumoniae develop resistance to these drugs by introducing mutations into key PBPs, generating enzymes that are recalcitrant to recognition by beta-lactams but that can still catalyze transpeptidation.

Model depicting the potential localization of proteins involved in bacterial cell wall formation: FtsZ, Z; FtsA, A; FtsK, K; FtsW, W; PBP2x, 2x; PBP2a, 2a; DivIB, IB; FtsL, L; DivIC, IC; PBP3, 3; RodA, RA; PBP2b, 2b; MreC, C; MreD, D; PcsB, B; PBP1a, 1a; PBP1b, 1b.

  • 3D structures of PBPs

      Our group in France was the first one to solve the structure of a PBP: PBP2x (Parès et al., 1996), and subsequently PBP3 (Morlot et al., 2005), PBP1b (Macheboeuf et al., 2005), PBP1a (Contreras-Martel et al., 2006, Job et al., 2008) and PBP2b (Contreras-Martel et al., 2009), all of them from S. pneumoniae (Fig.3). In addition, and in collaboration with groups from the Universities of Oxford and Liege, we identified the mechanism of action of gamma-lactam antibiotics (Fig.4). These results were published in Nature Chem. Biol. (Macheboeuf et al. 2007).

Structures cristallographiques des PBPs de S. pneumoniae résolues dans l’équipe.

The type III secretion system

Collaborations: I. Attree, iRTSV Grenoble; D. Lemaire, CEA Cadarache

The type III secretion system (T3SS) is a complex, multi-protein structure that plays a key role in the infectivity process of a number of Gram-negative pathogens. The system serves as a conduit to inject T3SS-specific toxins directly into the cytosol of target cells, bypassing periplasmic and extracellular steps, required in the case of other bacterial secretion systems. The T3SS is composed of over twenty macromolecules that associate into a basal structure spanning both bacterial membranes and is terminated by a hollow needle through which toxins are thought to travel in semi-unfolded state. Toxin entry into the target cytoplasm requires the formation of a proteinaceous pore (the translocon) on the eukaryotic membrane; the translocon is generally composed of two T3SS-encoded membrane proteins (the hydrophobic translocators) and one hydrophilic partner (the V antigen).

Scheme of the type III secretion system of Pseudomonas aeruginosa.

Most toxins, prior to their secretion through the T3SS needle, are maintained within the bacterial cytoplasm complexed to a dedicated chaperone. Interestingly, the two hydrophobic translocator proteins, in all human pathogenic species studied to date, are not recognized by two individual chaperones but rather share a common chaperone. Recently, our group solved the structure of PcrH complexed to a peptide from the membrane protein PopD (Fig.2A), from the pathogen Pseudomonas aeruginosa. The structure reveals that the peptide occupies the concave region of the TPR fold of PcrH, which was originally believed to be the bidning site for the main translocator (Fig.2B). Mutagenesis of PopD residues identified inthe structure as being anchor points for PcrH recognition compromised the intracellular stability of PopD in Pseudomonas strains, blocking secretion and cytotoxicity towards macrophages (Job et al., 2010).

(A) PcrH from Pseudomonas aeruginosa has a TPR fold. (B) The PopD peptide is localized within the concave region of the TPR structure (Job et al., 2010).


Neves D, Dessen A. (2012) Microbiology: Sensing stability. Nat Chem Biol., 8(8):681-2.

Neves D, Estrozi LF, Job V, Gabel F, Schoehn G and Dessen A. Conformational states of a bacterial alpha(2)-macroglobulin resemble those of human complement C3. PLoS One (2012) 7(4) : e35384

Gendrin C, Contreras-Martel C, Bouillot S, Elsen S, Lemaire D, Skoufias DA, Huber P, Attree I and Dessen A. Structural basis of cytotoxicity mediated by the type III secretion toxin exoU from Pseudomonas aeruginosa. PLoS Pathogens (2012) 8(4) : e1002637

El Mortaji L, Contreras-Martel C, Moschioni M, Ferlenghi I, Manzano C, Vernet T, Dessen A and Di Guilmi AM.The full-length Streptococcus pneumoniae major pilin RrgB crystallizes in a fiber-like structure, which presents the D1 isopeptide bond and provides details on the mechanism of pilus polymerization. Biochemical Journal (2012) 441(3) : 833-841

Nikolaidis I, Izore T, Job V, Thielens N, Breukink E and Dessen A
Calcium-dependent complex formation between PBP2 and lytic transglycosylase SltB1 of Pseudomonas aeruginosa. Microbial Drug Resistance (2012) 18(3) : 298-305

Tomašić T, Šink R, Zidar N, Fic A, Contreras-Martel C, Dessen A, Patin D, Blanot D, Müller-Premru M, Gobec S, Zega A, Kikelj D and Mašič LP. Dual inhibitor of MurD and MurE ligases from escherichia coli and staphylococcus aureus. ACS Medicinal Chemistry Letters (2012) 3(8) : 626-630

Contreras-Martel, C, Amoroso, A., Woon, E., Zervosen, A., Inglis, S, Martins, A., Verlaine, O., Rydzik, A., Job,V., Luxen, A., Joris, B., Schofield, C.J., and Dessen, A. (2011) Structure-guided design of cell wall biosynthesis inhibitors that overcome Beta-lactam resistance in Staphylococcus aureus (MRSA). ACS Chem. Biol. 6, 943-951.

Izoré, T., Job, V., and Dessen, A. (2011) Biogenesis, regulation, and targeting of the type III secretion system. Structure 19, 603-612.

Lebreton, A., Lakisic, G., Job, V., Fritsch, L., Tham, T.N., Camejo, A., et al., Dessen, A., Cossart, P., and Bierne,H. (2011) A bacterial protein targets the BAHD1 chromatin complex to stimulate type III interferon response. Science, 331, 1319-1320.

Matteï, P.-J., Neves, D., and Dessen, A. (2010) Bridging cell wall biosynthesis and bacterial morphogenesis. Curr. Opin. Struct. Biol. 20, 749-755.

Izoré, T., Contreras-Martel, C., El Mortaji, L., Manzano, C., Terrasse, R., Vernet, T., Di Guilmi, A.M., and Dessen, A. (2010) Structural basis of host cell recognition by the pilus adhesin from Streptococcus pneumoniae. Structure 18, 106-115.

Manzano, C., Contreras-Martel, C., El-Mortaji, L., Izoré, T., Vernet, T., Schoehn, G., Di Guilmi, A.M., and Dessen, A. (2008). Sortase-mediated pilus fiber formation in Streptococcus pneumoniae. Structure 16, 1838-1848.

Macheboeuf, P., Fischer, D., Zervosen, A., Luxen, A., Joris, B., Dessen, A.* and Schofield, C.* (2007) Structural and mechanistic basis of penicillin-binding protein inhibition by lactivicins. Nature Chem. Biol. 3, 565-569. (*corresponding authors).

Quinaud, M., Ple, S., Job, V., Contreras-Martel, C., Simorre, J.-P., Attree, I., and Dessen, A. (2007) Structure ofthe heterotrimeric complex that regulates type III secretion needle formation. Proc. Natl. Acad. Sci. USA 104,7803-7808.

Macheboeuf, P., Di Guilmi, A.M., Job, V., Vernet, T., Dideberg, O., and Dessen, A. (2005). Active site restructuring regulates ligand recognition in class A penicillin-binding proteins (PBPs). Proc. Natl. Acad. Sci.USA 102, 577-582.

Nanao, M.H., Tcherniuk SO, Chroboczek J, Dideberg O, Dessen A, Balakirev MY. (2004) Crystal structure of human otubain 2. EMBO Rep. 5, 783-788.

Dessen, A. (2004). A new catalytic dyad regulates anchoring of molecules to the Gram-positive cell wall by sortases. Structure 12, 6-7.

Schoehn, G., Di Guilmi, A.M., LeMaire, D., Attree, I., Weissenhorn, W., and Dessen, A. (2003). Oligomerization of type III secretion proteins PopB and PopD precedes pore formation in Pseudomonas. EMBO J. 22, 4957-4967.

Di Guilmi, A.M., and Dessen, A. (2002). New approaches towards the identification of antibiotic and vaccine targets in Streptococcus pneumoniae. EMBO Rep. 3, 728-734.

Dessen, A., Volchkov, V., Dolnik, O., Klenk, H.-D., and Weissenhorn, W. (2000). Crystal structure of the Ebola virus matrix protein VP40. EMBO J. 19, 4228-4236.

Dessen, A., Tang, J., Schmidt, H., Stahl, M., Clark, J. D., Seehra, J., and Somers, W. S. (1999) Crystal structure of human cytosolic phospholipase A2 reveals a novel topology and catalytic mechanism. Cell 97, 349-360.

Dessen, A., Lawrence, C. M., Cupo, S., Zaller, D. M., and Wiley, D. C. (1997) X-ray crystal structure of HLA-DR4 complexed with a peptide from human collagen II. Immunity 7, 473-481.

Weissenhorn, W., Dessen, A., Harrison, S.C., Skehel, J. J., and Wiley, D. C. (1997) Atomic structure of the ectodomain from HIV-1 gp41. Nature 387, 426-430.

Weissenhorn, W., Calder, L. J., Dessen, A., Laue, T., Skehel, J. J., and Wiley, D. C. (1997) Assembly of a rod-shaped chimera of a trimeric GCN4 zipper and the HIV-1 gp41 ectodomain expressed in Escherichia coli. Proc. Natl. Acad. Sci. USA 94, 6065-6069.

Dessen, A., Quémard, A., Blanchard, J. S., Jacobs Jr., W. R., and Sacchettini, J. C. (1995) Crystal structure and function of wild type and drug-resistant forms of the isoniazid target of Mycobacterium tuberculosis. Science 267, 1638-1641.


May 1993 Ph.D., Dept. of Biology, New York University, NY, USA

Aug 1987    B. Eng., Chemical Engineering, State University of Rio de Janeiro (UERJ), Brazil


Since Jan 2012   Researcher Group Scientific and administrative director of the Bacterial Pathogenesis group at the Institut de Biologie Structurale (IBS), Grenoble, France;

Since Oct 2005    CNRS Research director (Directeur de Recherches – DR2). IBS Grenoble, France


2006-2009   Scientific and administrative co-director, Membrane Protein Laboratory (LPM, 7 independent groups); Institut de Biologie Structurale (IBS), Grenoble

2001-2005   CNRS Researcher (Chargé de Recherches – CR1), IBS, Grenoble

1999-2000   Visiting scientist at the EMBL Grenoble; consultant in crystallography for Wyeth Research, Cambridge, MA, USA

1997-1999   Staff scientist in X-ray crystallography, Wyeth Research, Cambridge, MA, USA

1995-1997   Postdoctoral scientist with Don C. Wiley, Harvard University; Boston, MA, USA

1993-1995   Postdoctoral researcher, Albert Einstein College of Medicine, New York, USA

1987-1993   Ph.D student, New York University, New York, USA

1987-1989   Research assistant, New York University, Chemistry Dept.

1985-1987   Research assistant, Electrical Energy Research Center (CEPEL), Rio de Janeiro, Brazil