Articles by Idir Malki in JoVE
Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins Clément Danis*1,2, Clément Despres*1, Luiza M. Bessa1, Idir Malki1, Hamida Merzougui1, Isabelle Huvent1, Haoling Qi1, Guy Lippens1, François-Xavier Cantrelle1, Robert Schneider1, Xavier Hanoulle1, Caroline Smet-Nocca1, Isabelle Landrieu1 1UMR8576, CNRS, Lille University, 2UMR-S1172, INSERM CNRS, Lille University We describe here a method to identify multiple phosphorylations of an intrinsically disordered protein by Nuclear Magnetic Resonance Spectroscopy (NMR), using Tau protein as a case study. Recombinant Tau is isotopically enriched and modified in vitro by a kinase prior to data acquisition and analysis.
Other articles by Idir Malki on PubMed
(1)H, (13)C and (15)N Resonance Assignments of the Periplasmic Signalling Domain of HasR, a TonB-dependent Outer Membrane Heme Transporter Biomolecular NMR Assignments. Apr, 2013 | Pubmed ID: 22415545 TonB-dependent transporters (TBDTs) are bacterial outer membrane proteins that internalize nutrients such as vitamin B12, metal complexes, heme, some carbohydrates, etc. In addition to their transport activity, several TBDTs are also involved in a signalling cascade from the cell surface into the cytoplasm, via their periplasmic signalling domain. Here we report the backbone and side chain resonance assignments of the signalling domain of HasR, a TonB-dependent outer membrane heme transporter from Serratia marcescens as a first step towards its structural study.
Interaction of a Partially Disordered Antisigma Factor with Its Partner, the Signaling Domain of the TonB-dependent Transporter HasR PloS One. 2014 | Pubmed ID: 24727671 Bacteria use diverse signaling pathways to control gene expression in response to external stimuli. In Gram-negative bacteria, the binding of a nutrient is sensed by an outer membrane transporter. This signal is then transmitted to an antisigma factor and subsequently to the cytoplasm where an ECF sigma factor induces expression of genes related to the acquisition of this nutrient. The molecular interactions involved in this transmembrane signaling are poorly understood and structural data on this family of antisigma factor are rare. Here, we present the first structural study of the periplasmic domain of an antisigma factor and its interaction with the transporter. The study concerns the signaling in the heme acquisition system (Has) of Serratia marcescens. Our data support unprecedented partially disordered periplasmic domain of an anti-sigma factor HasS in contact with a membrane-mimicking environment. We solved the 3D structure of the signaling domain of HasR transporter and identified the residues at the HasS-HasR interface. Their conservation in several bacteria suggests wider significance of the proposed model for the understanding of bacterial transmembrane signaling.
Structural Basis of the Signalling Through a Bacterial Membrane Receptor HasR Deciphered by an Integrative Approach The Biochemical Journal. Jul, 2016 | Pubmed ID: 27208170 Bacteria use diverse signalling pathways to adapt gene expression to external stimuli. In Gram-negative bacteria, the binding of scarce nutrients to membrane transporters triggers a signalling process that up-regulates the expression of genes of various functions, from uptake of nutrient to production of virulence factors. Although proteins involved in this process have been identified, signal transduction through this family of transporters is not well understood. In the present study, using an integrative approach (EM, SAXS, X-ray crystallography and NMR), we have studied the structure of the haem transporter HasR captured in two stages of the signalling process, i.e. before and after the arrival of signalling activators (haem and its carrier protein). We show for the first time that the HasR domain responsible for signal transfer: (i) is highly flexible in two stages of signalling; (ii) extends into the periplasm at approximately 70-90 Å (1 Å=0.1 nm) from the HasR β-barrel; and (iii) exhibits local conformational changes in response to the arrival of signalling activators. These features would favour the signal transfer from HasR to its cytoplasmic membrane partners.