Liliane Assairi

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Bacterial UMP kinases are essential enzymes involved in the multistep synthesis of nucleoside triphosphates. They are hexamers regulated by the allosteric activator GTP and inhibited by UTP. We solved the crystal structure of Escherichia coli UMP kinase bound to the UMP substrate (2.3 A resolution), the UDP product (2.6 A), or UTP (2.45 A). The monomer(More)
Centrins are well-conserved calcium binding proteins from the EF-hand superfamily implicated in various cellular functions, such as centrosome duplication, DNA repair, and nuclear mRNA export. The intrinsic molecular flexibility and the self-association tendency make difficult the structural characterization of the integral protein. In this paper we report(More)
In this work, we examined the regulation by GTP and UTP of the UMP kinases from eight bacterial species. The enzyme from Gram-positive organisms exhibited cooperative kinetics with ATP as substrate. GTP decreased this cooperativity and increased the affinity for ATP. UTP had the opposite effect, as it decreased the enzyme affinity for ATP. The nucleotide(More)
hSfi1, a human centrosomal protein with homologs in other eukaryotic organisms, includes 23 repeats, each of 23 amino acids, separated by 10 residue linkers. The main molecular partner in the centrosome is a small, calcium-binding EF-hand protein, the human centrin 2. Using isothermal titration calorimetry experiments, we characterized the centrin-binding(More)
Centrins are calcium binding proteins that belong to the EF-hand (or calmodulin) superfamily, which are highly conserved among eukaryotes. Herein, we report the molecular features and binding properties of the green alga Scherffelia dubia centrin (SdCen), a member of the Chlamydomonas reinhardtii centrin (CrCen) subfamily. The Ca(2+) binding capacity of(More)
The gene encoding Bacillus subtilis UMP kinase (pyrH/smbA) is transcribed in vivo into a functional enzyme, which represents approximately 0.1% of total soluble proteins. The specific activity of the purified enzyme under optimal conditions is 25 units.mg-1 of protein. In the absence of GTP, the activity of B. subtilis enzyme is less than 10% of its maximum(More)
Centrin, an EF-hand calcium-binding protein, has been shown to be involved in the duplication of centrosomes, and Sfi1 (Suppressor of fermentation-induced loss of stress resistance protein 1) is one of its centrosomal targets. There are three isoforms of human centrin, but here we only considered centrin 2 (HsCen2). This protein has the ability to bind to(More)
The effects of progesterone on lactose synthesis activity and changes in mammary gland cells were studied in pseudopregnant rabbits simultaneously treated with prolactin. The injection of progesterone alone on Days 15 and 17 of pseudopregnancy decreased the activity of lactose synthetase (LSA) and galactosyl transferase (GTA), while the administration of(More)
Bacterial cytidine monophosphate (CMP) kinases are characterised by an insert enlarging their CMP binding domain, and by their particular substrate specificity. Thus, both CMP and 2'-deoxy-CMP (dCMP) are good phosphate acceptors for the CMP kinase from Escherichia coli (E. coli CMPK), whereas eukaryotic UMP/CMP kinases phosphorylate the deoxynucleotides(More)
Here we describe the crystal structures of the NAD kinase (LmNADK1) from Listeria monocytogenes in complex with its substrate NAD, its product NADP, or two synthesized NAD mimics. We identified one of the NAD mimics, di-adenosine diphosphate, as a new substrate for LmNADK1, whereas we showed that the closely related compound di-5'-thioadenosine is a novel(More)