Research
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Separation of daughter cells during bacterial cell division requires that the septal cross wall be split by peptidoglycan hydrolases. In Streptococcus pneumoniae an essential protein termed PcsB is predicted to perform this critical operation. Recent evidence shows that the activity of PcsB is regulated by the transmembrane FtsEX complex. In this work the muralytic activity of PcsB is demonstrated for the first time. Furthermore, we report the crystal structure of full-length PcsB showing an unprecedented dimeric structure in which the unique V-shaped coiled-coil domain of each monomer acts as a molecular tweezers locking down the catalytic domain of its dimeric partner in an inactive configuration. This finding strongly suggests that the release of the catalytic domains requires an ATP-driven conformational change in the FtsEX complex, which is most likely conveyed towards the catalytic domains through a set of coordinated movements of the α-helices forming the coiled-coil domain of PcsB.
Sergio G. Bartual, Daniel Straume, Gro Anita Stamsås, Inés G. Muñoz, Carlos Alfonso, Martín Martínez-Ripoll, Leiv Sigve Håvarstein* & Juan A. Hermoso *
Structural basis of PcsB-mediated cell separation in Streptococcus pneumoniae
Nature Communications (2014). DOI: 10.1038/ncomms4842
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"Pablo García-Risueño started his work on this subject when doing his PhD at the institute."
The problem of the electrostatic potential is almost ubiquituous in chemical and atomic/molecular simulations. In this paper just published at the Journal of Computational Chemistry (and appearing at its front cover), Pablo García-Risueno et al. present an analysis of different methods to calculate the classical electrostatic Hartree potential created by charge distributions. This work may enable more accurate and efficient simulations, helping scientists to tackle many new systems.
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Metabolic resistance to insecticides is the biggest threat to the continued effectiveness of malaria vector control. In the frame of a transnational research program, we have demonstrated that a single amino acid change in the glutathione-s-transferase confers high levels of DDT resistance in the African mosquito Anopheles funestus. Interestingly, this metabolic resistance marker perfectly correlates with patterns of DDT resistance across Africa. The x-ray structures of two polymorphic GSTe2 corresponding to those populations presenting an intensified resistance or sensitiveness phenotypes show that the mutation confers resistance by enlarging the GSTe2 DDT-binding cavity leading to increased DDT access and metabolism. This knowledge constitutes a valuable tool for future operational monitoring of insecticide resistance in Africa and allows us to design novel molecules with enhanced insecticide properties.
Reference:
Riveron JM, Yunta C, Ibrahim SS, Djouaka R, Irving H, Menze BD, Ismail HM, Hemingway J, H. Ranson, A. Albert and C.S. Wondji
Genome Biology 2014, 15:R27 (25 February 2014)
Highlighted at:
Insecticide resistance comes of age (ffrench-Constant RH Genome Biology 2014, 15:106 (25 February 2014))
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The respiratory pathogen Streptococcus pneumoniae has evolved efficient mechanisms to resist oxidative stress conditions and to displace other bacteria in the nasopharynx. Here we characterize at physiological, functional and structural levels two novel surface-exposed thioredoxin-family lipoproteins, Etrx1 and Etrx2. The impact of both Etrx proteins and their redox partner methionine sulfoxide reductase SpMsrAB2 on pneumococcal pathogenesis was assessed in mouse virulence studies and phagocytosis assays. The results demonstrate that loss of function of either both Etrx proteins or SpMsrAB2 dramatically attenuated pneumococcal virulence in the acute mouse pneumonia model and that Etrx proteins compensate each other. The deficiency of Etrx proteins or SpMsrAB2 further enhanced bacterial uptake by macrophages, and accelerated pneumococcal killing by H2O2 or free methionine sulfoxides (MetSO). Moreover, the absence of both Etrx redox pathways provokes an accumulation of oxidized SpMsrAB2 in vivo. Taken together our results reveal insights into the role of two extracellular electron pathways required for reduction of SpMsrAB2 and surface-exposed MetSO. Identification of this system and its target proteins paves the way for the design of novel antimicrobials.
Reference:
Malek Saleh, Sergio G. Bartual, Mohammed R. Abdullah, Inga Jensch, Tauseef M. Asmat, Lothar Petruschka, Thomas Pribyl, Juan A. Hermoso* and Sven Hammerschmidt*
Molecular architecture of Streptococcus pneumoniae surface thioredoxin-fold lipoproteins crucial for extracellular oxidative stress resistance and maintenance of virulence
EMBO Molecular Medicine (2013) 5, 1852-1870 (doi:10.1002/emmm.201202435)
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The alpha/beta hydrolase fold is one of the most versatile structures in the protein realm according to the diversity of sequences adopting such a three dimensional architecture. We found that the versatility of a canonical alpha/beta-hydrolase fold, particularly that of the carboxylesterase Cest-2923 from the lactic acid bacterium Lactobacillus plantarum WCFS1, also extends to its oligomeric behavior in solution. Thus, we discovered that Cest-2923 exhibits a pH-dependent pleomorphic behaviour in solution involving monomers, canonical dimers and tetramers. Whereas at neutral pH the system is mainly shifted to dimeric species, at acidic conditions tetrameric species predominate. Interestingly, despite that these tetramers result from the association of canonical dimers, as commonly found in many other carboxylesterases from the hormone-sensitive lipase family, they can be defined as “non canonical” since they represent a different association mode. The observed associative behaviour is consistent with different crystallographic results of Cest-2923 from structural genomics consortia. Finally, we benefit from the presence of sulphate or acetate molecules (depending on the crystal form analysed) in the close vicinity of the nucleophile Ser116, to identify interactions with the putative oxyanion hole and also to deduce the existence of hydrolytic activity within Cest-2923 crystals.
Reference:
Benavente R, Esteban-Torres M, Acebrón I, de Las Rivas B, Muñoz R, Alvarez Y, Mancheño JM. “Structure, biochemical characterization and analysis of the pleomorphism of carboxylesterase Cest-2923 from Lactobacillus plantarum WCFS1”. FEBS J. 2013 Oct 16. doi: 10.1111/febs.12569.
