The Rosalind Franklin Institute is welcoming Professor Teresa Carlomagno on Thursday 11th December from 11:00 – 12:00.

Talk title:

An integrative structural biology approach to understand functional mechanisms in biological complexes

Abstract:

After >60 years of structural biology, the complexity of both the molecules we study and the questions we pose has increased enormously. Nowadays, we aim to achieve complete spatial/temporal characterization of large molecular complexes during their function, as well as understand the functional mechanisms of disorder and the role of conformational dynamics. In this context, the direction of travel for structural biology is towards integrative methods, where complementarities across cutting-edge technologies are leveraged to address more challenging systems and to understand functional mechanisms in greater depth.

Magnetic resonance makes vital contributions across physical, biological and medical fields, due to its unique ability to study molecules in both the spatial and temporal dimensions, reveal minorly-populated conformations and cope with structural disorder. Furthermore, methyl TROSY and 15N,13C-direct-detection experiments allow molecular species as large as 1 MDa to be interrogated by solution NMR.

In our laboratory, we use and develop integrative structural biology approaches that employ NMR together with complementary methods to understand the functional mechanism of high-molecular-weight complexes with enzymatic activity. Integrative structural biology in solution is particularly relevant for enzymes that contain disordered parts and for transiently forming complexes, where X-ray crystallography or electron microscopy fail.

I will demonstrate the approach on the example of a multi-protein complex responsible for acetylation of histone H3. The complex consists of the fungal histone acetyltransferase Rtt109, the histone chaperones Asf1 and Vps75 and the H3:H4 histone dimer. Rtt109 is required for histone H3 K9, K27 and K56 acetylation in fungi and is thus an attractive drug target in the fight of fungal infections. Rtt109 activity requires two structurally unrelated histone chaperones, Asf1 and Vps75. These proteins activate Rtt109 via different mechanisms, with Rtt109 –Asf1 association being necessary for K56 acetylation, and Rtt109­–Vps75 association being required for K9 acetylation.

Using our integrative structural biology approach, we explain how Vps75 promotes acetylation of residues in the H3 N-terminal tail: the chaperone engages the disordered H3 tail in fuzzy electrostatic interactions with its own disordered C-terminal domain and thereby confines the H3 tail to a wide cavity faced by the Rtt109 active site. These fuzzy interactions between disordered domains achieve localization of the H3 tail to the catalytic site with minimal loss of entropy, and may represent a universal mechanism for substrate localization in enzymatic reactions involving long, highly-disordered substrates.

Biography:

Teresa Carlomagno is an internationally recognized expert in the development and application of integrative structural biology (ISB) to biomolecular complexes. She has dedicated her scientific life to studying how molecular partners communicate with each other; in this mission her research has been pushing the limits of structural biology techniques in solution to address questions of constantly higher complexity.

In recent years structural biology has expanded to include the notion that some molecules do not have a well-defined shape but are rather malleable; these molecules can interact with predefined three-dimensional structures by adapting to them, similar to pieces of playdough. Even more recently, efficient and functional interactions have been demonstrated to exist between spaghetti-like molecules, which are able to bind tightly to each other while preserving their disorder (as in a tangle of ropes). In her research, Teresa Carlomagno uses ISB to understand how these flexible molecular complexes form, execute tasks and disassociate. She characterizes intermolecular interactions at the border between structure, dynamics and disorder by combining NMR spectroscopy both in solution and in solid-state with XRS, EM, Small-Angle-Scattering (SAS) and Electron Paramagnetic Resonance (EPR). In parallel, she develops the computational methodologies necessary to interpret and evaluate ISB data.

To watch the seminar online, please sign up via the link below.

RAL site pass holders are welcome to attend in person (no registration required) in the Franklin’s first floor Hub. To join in person, please arrive in the R113 Franklin foyer at least 5 minutes before the start of the seminar and a member of the team will let you into the building.