xtal

At PCISBIO meeting

XTAL members were attending the meeting of the Portuguese Centre for Integrated Structural Biology. Today, at ITQB.

Great words, Maria João!

Maria João's interview at Encontro CIÊNCIA 2018

https://www.youtube.com/watch?v=czLt-sl2X30&feature=share

At the International Iberian Biophysics Congress, in Castelló de la Plana, Spain

Xtal member Ana Luisa Carvalho has just presented her work in the International Iberian Biophysics Congress!

Kumar, K, Correia M, Pires VR, Dhillon A, Sharma K, Rajulapati V, Fontes CMGA, Carvalho AL, Goyal A.  2018.  Novel insights into the degradation of β-1,3-glucans by the cellulosome of Clostridium thermocellum revealed by structure and function studies of a family 81 glycoside hydrolase. International Journal of Biological Macromolecules. :-. AbstractWebsite

Abstract The family 81 glycoside hydrolase (GH81) from Clostridium thermocellum is a β-1,3-glucanase belonging to cellulosomal complex. The gene encoding \{GH81\} from Clostridium thermocellum (CtLam81A) was cloned and expressed displaying a molecular mass of  82 kDa. CtLam81A showed maximum activity against laminarin (100 U/mg), followed by curdlan (65 U/mg), at pH 7.0 and 75 °C. CtLam81A displayed Km, 2.1 ± 0.12 mg/ml and Vmax, 109 ± 1.8 U/mg, against laminarin under optimized conditions. CtLam81A activity was significantly enhanced by Ca2+ or Mg2+ ions. Melting curve analysis of CtLam81A showed an increase in melting temperature from 91 °C to 96 °C by Ca2+ or Mg2+ ions and decreased to 82 °C by EDTA, indicating that Ca2+ and Mg2+ ions may be involved in catalysis and in maintaining structural integrity. \{TLC\} and MALDI-TOF analysis of β-1,3-glucan hydrolysed products released initially, showed β-1,3-glucan-oligosaccharides degree of polymerization (DP) from \{DP2\} to DP7, confirming an endo-mode of action. The catalytically inactive mutant CtLam81A-E515A generated by site-directed mutagenesis was co-crystallized and tetragonal crystals diffracting up to 1.4 Å resolution were obtained. CtLam81A-E515A contained 15 α-helices and 38 β-strands forming a four-domain structure viz. a β-sandwich domain I at N-terminal, an α/β-domain II, an (α/α)6 barrel domain III, and a small 5-stranded β-sandwich domain IV.

Leisico, F, V. Vieira D, Figueiredo TA, Silva M, Cabrita EJ, Sobral RG, Ludovice AM, Trincão J, Romão MJ, de Lencastre H, Santos-Silva T.  2018.  First insights of peptidoglycan amidation in Gram-positive bacteria - the high-resolution crystal structure of Staphylococcus aureus glutamine amidotransferase GatD, 2018. Scientific Reports. 8(1):5313. AbstractWebsite

Gram-positive bacteria homeostasis and antibiotic resistance mechanisms are dependent on the intricate architecture of the cell wall, where amidated peptidoglycan plays an important role. The amidation reaction is carried out by the bi-enzymatic complex MurT-GatD, for which biochemical and structural information is very scarce. In this work, we report the first crystal structure of the glutamine amidotransferase member of this complex, GatD from Staphylococcus aureus, at 1.85 Å resolution. A glutamine molecule is found close to the active site funnel, hydrogen-bonded to the conserved R128. In vitro functional studies using 1H-NMR spectroscopy showed that S. aureus MurT-GatD complex has glutaminase activity even in the absence of lipid II, the MurT substrate. In addition, we produced R128A, C94A and H189A mutants, which were totally inactive for glutamine deamidation, revealing their essential role in substrate sequestration and catalytic reaction. GatD from S. aureus and other pathogenic bacteria share high identity to enzymes involved in cobalamin biosynthesis, which can be grouped in a new sub-family of glutamine amidotransferases. Given the ubiquitous presence of GatD, these results provide significant insights into the molecular basis of the so far undisclosed amidation mechanism, contributing to the development of alternative therapeutics to fight infections.

New paper online!

New paper online!

Bule, P, Pires VMR, Alves VD, Carvalho AL, Prates JAM, Ferreira LMA, Smith SP, Gilbert HJ, Noach I, Bayer EA, Najmudin S, Fontes CMGA.  2018.  Higher order scaffoldin assembly in Ruminococcus flavefaciens cellulosome is coordinated by a discrete cohesin-dockerin interaction, 2018. Scientific Reports. 8(1):6987. AbstractWebsite

Cellulosomes are highly sophisticated molecular nanomachines that participate in the deconstruction of complex polysaccharides, notably cellulose and hemicellulose. Cellulosomal assembly is orchestrated by the interaction of enzyme-borne dockerin (Doc) modules to tandem cohesin (Coh) modules of a non-catalytic primary scaffoldin. In some cases, as exemplified by the cellulosome of the major cellulolytic ruminal bacterium Ruminococcus flavefaciens, primary scaffoldins bind to adaptor scaffoldins that further interact with the cell surface via anchoring scaffoldins, thereby increasing cellulosome complexity. Here we elucidate the structure of the unique Doc of R. flavefaciens FD-1 primary scaffoldin ScaA, bound to Coh 5 of the adaptor scaffoldin ScaB. The RfCohScaB5-DocScaA complex has an elliptical architecture similar to previously described complexes from a variety of ecological niches. ScaA Doc presents a single-binding mode, analogous to that described for the other two Coh-Doc specificities required for cellulosome assembly in R. flavefaciens. The exclusive reliance on a single-mode of Coh recognition contrasts with the majority of cellulosomes from other bacterial species described to date, where Docs contain two similar Coh-binding interfaces promoting a dual-binding mode. The discrete Coh-Doc interactions observed in ruminal cellulosomes suggest an adaptation to the exquisite properties of the rumen environment.

Congrats, Raquel!

Gomes, AS, Trovão F, Andrade Pinheiro B, Freire F, Gomes S, Oliveira C, Domingues L, Romão MJ, Saraiva L, Carvalho AL.  2018.  The Crystal Structure of the R280K Mutant of Human p53 Explains the Loss of DNA Binding. International Journal of Molecular Sciences. 19, Number 4}, ARTICLE NUMBER = {1184 AbstractWebsite

The p53 tumor suppressor is widely found to be mutated in human cancer. This protein is regarded as a molecular hub regulating different cell responses, namely cell death. Compelling data have demonstrated that the impairment of p53 activity correlates with tumor development and maintenance. For these reasons, the reactivation of p53 function is regarded as a promising strategy to halt cancer. In the present work, the recombinant mutant p53R280K DNA binding domain (DBD) was produced for the first time, and its crystal structure was determined in the absence of DNA to a resolution of 2.0 Å. The solved structure contains four molecules in the asymmetric unit, four zinc(II) ions, and 336 water molecules. The structure was compared with the wild-type p53 DBD structure, isolated and in complex with DNA. These comparisons contributed to a deeper understanding of the mutant p53R280K structure, as well as the loss of DNA binding related to halted transcriptional activity. The structural information derived may also contribute to the rational design of mutant p53 reactivating molecules with potential application in cancer treatment.

New paper online!

The Xtal group in ExpoFCT

Marino and Bruno are introducing secondary school students to the potentialities of crystallography.

Branco, PS, Peixoto D, Figueiredo M, Malta G, Roma-Rodrigues C, Batista PV, Fernandes AR, Barroso S, Carvalho AL, Afonso CAM, Ferreira LM.  2018.  Synthesis, cytotoxicity evaluation in human cell lines and in vitro DNA interaction of a hetero arylidene-9(10H)-anthrone. European Journal of Organic Chemistry. :n/a–n/a. AbstractWebsite

A new and never yet reported hetero arylidene-9(10H)-anthrone structure (4) was unexpectedly isolated on reaction of 1,2-dimethyl-3-ethylimidazolium iodide (2) and 9-anthracenecarboxaldehyde (3) under basic conditions. Its structure was unequivocally attributed by X-ray crystallography. No cytotoxicity in human healthy fibroblasts and in two different cancer cell lines was observed indicating its applicability in biological systems. Compound 4 interacts with CT-DNA by intercalation between the adjacent base pairs of DNA with a high binding affinity (Kb = 2.0(± 0.20) x 105 M-1) which is 10x higher than that described for doxorubicin (Kb = 3.2 (±0.23) × 104 M-1). Furthermore, compound 4 quenches the fluorescence emission of GelRed-CT-DNA system with a quenching constant (KSV) of 3.3(±0.3) x 103 M-1 calculated by the Stern-Volmer equation.

Ribeiro, DO, Pinheiro BA, Carvalho AL, Palma AS.  2018.  Targeting protein-carbohydrate interactions in plant cell-wall biodegradation: the power of carbohydrate microarrays. Carbohydrate Chemistry: Chemical and Biological Approaches Volume 43. 43:159-176.: The Royal Society of Chemistry Abstract

The plant cell-wall is constituted by structurally diverse polysaccharides. The biodegradation of these is a crucial process for life sustainability. Cellulolytic microorganisms are highly efficient in this process by assembling modular architectures of carbohydrate-active enzymes with appended non-catalytic carbohydrate-binding modules (CBMs). Carbohydrate microarrays offer high-throughput and sensitive tools for uncovering carbohydrate-binding specificities of CBMs{,} which is pivotal to understand the function of these modules in polysaccharide biodegradation mechanisms. Features of this technology will be here briefly reviewed with highlights of microarray approaches to study plant-carbohydrates and CBM-carbohydrate interactions{,} along with an overview of plant polysaccharides and microorganisms strategies for their recognition.

New book chapter!

Congratulations, Rita!

PhD student Ana Rita Otrelo Cardoso is at this moment defending her PhD thesis work entitled "Structural studies on molybdenum-dependent enzymes: from transporters to enzymes", co-supervised by Teresa Santos Silva and Maria João Romão. Well done, Rita! We're all very proud of your work!

Congrats, Diana!


Today, PhD student Diana Ribeiro publicly presented her PhD Workplan to the Thesis Advisory Committee. Congratulations, Diana, your thesis is in the right track!

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