Lo Leggio Group - Crystallography

My group focuses on structural chemistry and in particular the structure of biological macromolecules.

Research focus

We are primarily interested in proteins and their interactions with other proteins, carbohydrates and DNA. We use crystallography as the primary technique for structure determination, including method development.

In order to determine how protein structure dictates biological function we complement crystallography with protein chemistry, biochemical and other biophysical techniques.

Current and recent projects focus on carbohydrate modifying enzymes that can help in the green transition or are involved in disease, bacteriophage regulators, and protonation state of proteins.

Group leader

Leila Lo Leggio
Professor
Office: C310

Research

My group works on macromolecules structure and function, primarily proteins, in particular enzymes, and their interactions with each other and other macromolecules (nuclei acids and polysaccharides).

Biomass is an important renewable resource, and much of it is composed by polysaccharides, especially when coming from plants, like in food or agricultural waste.

These polysaccharides are often crystalline and embedded in complex matrices also involving other components like lignin, leading to high recalcitrance to breakdown.

This is an obstacle for using renewable resources for producing eg bioethanol or biomaterials. In my group we study the mechanisms of enzymes involved in plant biomass degradation at the atomic level, as well as their interactions with complex plant biomass components.

We study for example glycoside hydrolases, lytic polysaccharide monooxygenases and glucuronoyl esterases. Below an example of a covalent intermediate trapped in a variant of a glucuronyl esterase, and enzyme involved in decoupling lignin and polysaccharides.

In the paper, part of an ongoing collaboration with Johan Larsbrink at Chalmers University of Technology, we use crystallography, biochemistry and computation to better understand the mechanism and learn to utilize these enzymes beneficially.

From Zong et al Nature communications 13,1449 (2022)

‘Mechanism and biomass association of glucuronoyl esterase: an α/β hydrolase with potential in biomass conversion’

The other main research theme in my lab are DNA binding transcription factors, particularly the ones involved in lysogeny-lysis switches.

These switches decide whether temperate phages go into the lysogenic or lytic cycle (killing the bacteria) and they are important in transfer of genetic material between bacteria.

We are particularly interested in switches involving the CI-MOR protein-protein interaction shown below, particularly the ones from Gram-positive pathogenic bacteria bacteriophages (like the Staphylococcus aureus phi13 phage).

In these projects we collaborate with other structural biologists and microbiologists.

CI-NTD-MOR crystal structure as elucidated in Rasmussen et al. PNAS 117 (34) 20576-20585 (2020)

Rasmussen et al. PNAS 117 (34) 20576-20585 (2020) ‘Revealing the mechanism of repressor inactivation during switching of a temperate bacteriophage’

Although we use many techniques, our favourite is crystallography. Aside from ‘just’ determining structures of proteins and their interaction with small and large molecules as in the example above, we also use more advanced crystallography. For example:

High resolution crystallography to determine the protonation state of residues in enzymes (read more here)

Our recent detailed work on X-ray induced photoreduction of lytic polysaccharide monooxygenases (read more here)

We are avid users of synchrotron facilities like:

MAX IV

ESRF

We cooperate with several facility scientists. I also work very closely with the other crystallographers in the Biological Chemistry Section:

I am also a member of:

ISBUC

The Centre for Medicinal Chemistry at the University of Copenhagen

Projects

In a typical project, you might produce and/or crystallize a protein/enzyme alone or in complex with other macromolecules or small ligands, and then determine its structure by crystallography, or use complementary techniques to gain structural and functional information.

These are core methods used in structure-based drug design and protein engineering in industry.

In a current project, we apply enzymes to make environmentally friendly plasticizers. Projects focusing on computational analysis or fundamental methods can be arranged.

If you are interested in understanding how structure and chemistry make biological macromolecules function, we can probably find a project to fit your specialization.

Collaborations

We collaborate with many bio-chemistry groups in Denmark and the world, for example Chalmers University in Sweden.

We also collaborate with researchers at synchrotron and neutron diffraction facilities.

Many of the projects you can be involved in are part of such collaborations, so you will most likely meet and work with scientists from diverse backgrounds, physically or virtually.