|External Faculty Speaker|
|External Faculty Speaker|
|External Faculty Speaker||
Abstract: Characterising the assembly of large nanomachines using native MS
Native mass spectrometry (MS) is a remarkable tool for investigating non-covalent complexes with high sensitivity, accuracy and selectivity. The mass of intact assemblies, their precise stoichiometry, the direct binding between subunits and the position of subunits within the complex (core and peripheral ones) can be established. By mixing subunits, a hierarchy in assembly of a complex can be determined. Native MS complements structural methods (e.g. NMR and EM) because it requires little quantities of sample, tolerates heterogeneity of subunit composition, does not require crystals or labelling and symmetry in the structure does not represent an advantage.
In my seminar I will illustrate different applications of native MS. For example, we study a human hetero-assembly: the SAGA complex, whose precise stoichiometry is not fully characterised. We also investigate the assembly pathway of two nanomachines: a large bacterial homo-complex and a viral protein-RNA hetero-complex. Regarding the homo-complex we aim at elucidating the mechanism of its self-assembly. To better monitor the first events during self-assembly, we use “isotopic hybridization” and MS. Determining the mass and stoichiometry of the hybrid complex allows us to identify the intermediate present at the beginning of the self-assembly reaction. MS data are complemented by NMR used to probe conformational changes of subunits during the complex assembly.
Regarding the hetero-complex we study an assembly formed by RNA, viral and human proteins. Native MS allows us not only to investigate the stoichiometry of the holo- and apo- complexes, but also to characterise the effect of the RNA in terms of complex stability. By MS we can also identify which proteins should be present in the assembly before other proteins can be added.
To conclude, native MS represents an innovative approach for characterising the assembly pathway of homo- and hetero-complexes in a time-resolved manner.
|Science and Society||Abstract: La vie a commencé dans les oceans il y a 4 milliards d’années et les étapes majeures de l’évolution s’y sont déroulées avant l’apparition de la vie terrestre. Ce sont ces écosystèmes qui ont produit l’oxygène nécessaire à l’apparition des mammifères. Pourtant nous ne connaissons pratiquement rien d'eux. Je vais expliquer comment l’expédition TARA OCEANS va permettre de mieux caractériser ces écosystèmes, leur diversité, leur évolution et leur rôle dans l’économie globale de notre planète.|