Our structural biology programme at the crossroad of genetic diseases and drug discovery

The MOB group combines structural, biochemical, and chemical biology approaches to explore how genetic defects lead to disease at a protein molecular level. The group has determined to date > 60 crystal structures of human enzymes and complexes that are associated with Inborn Errors of Metabolism. We form a partnership network with 'front-line' geneticists, clinicians and drug developers in the field of rare diseases, aimed at deciphering the underlying genetic, biochemical and cellular disease mechanisms, as a first step towards developing novel disease-transforming therapeutics.

Our key areas of research interest include:

Small molecule therapy by substrate reduction

Disease-associated metabolic enzymes often lead to aberrant flux and accumulation of toxic metabolites. Therefore, pathway manipulation to reduce flux to the defective enzyme could have therapeutic benefit, as shown for lysosomal storage disorders. Our objectives are to develop small molecule inhibitors for enzymes upstream of a metabolic defect, as  'substrate reduction therapy'.

Through the Wellcome Strategy Award programme (2015-2020) funded to the SGC, we develop ‘target enabling packages (TEPs)’ for disease-linked proteins where there is a need for novel therapies. These packages include recombinant reagents, crystal structures, biophysical assays, and chemical ligands – data that validate the target protein for therapeutic intervention and tools that serve as starting point for medicinal chemistry programme. To date our group has delivered TEPs in the metabolic disorders for AASS (pyridoxine dependent epilepsy) and HAO1 (primary hyperoxaluria) - both adopting the substrate reduction approach.

Our datasheet for the Target Enabling Package on AASS enzyme, target for pyridoxine-dependent epilepsy

Our datasheet for the Target Enabling Package on HAO1 enzyme, target for Primary Hyperoxaluria; follow our LIVE open lab notebook on developing HAO1 inhibitors

 Our datasheet for the Target Enabling Package on GALK1/GALT enzymes, to study classic galactosemia

 Our datasheet for the Target Enabling Package on ALAS2, target for erythroid porphyria

Structural characterization of metabolic enzyme complexes

Many metabolic enzymes performing essential cellular roles do not exist as individual entities, but instead function in concert with other proteins in the cellular compartment. These partner proteins within a macromolecular complex could be ‘functional neighbours’ performing the upstream/ downstream chemical reactions within a metabolic pathway, or accessory subunits responsible for the structural integrity and functional modulation of the target enzyme. As part of our rare disease research programme, we have a vested interest in studying metabolic enzyme complexes that are linked with genetic diseases. We adopt the co-expression approach to generate metabolic enzyme complexes for structural, biochemical and biophysical experiments aimed at characterizing the functional and disease-causing mechanisms.

 Structure of the molybdenum synthase complex MOCS2A-MOCS2B

 Our recent structure of the human frataxin-bound iron-sulphur cluster assembly complex published in Nature Communications

Glycogen biosynthesis and storage disorders

In eukaryotes, glycogen biosynthesis involves the priming enzyme glycogenin (GYG1/2), the elongation enzyme glycogen synthase (GYS1/2), and the branching enzyme (GBE1). We have captured crystallographic snapshots of the human glycogenin dimer along its reaction cycle, revealing a dynamic conformational switch between ground and active states mediated by the sugar donor UDP-glucose. This work provides a new look into how glucose units are attached covalently to glycogenin during the initial step of glycogen synthesis. 

Mutations on the GBE1 gene lead to an extremely heterogeneous form of glycogen storage disorder type IV, including an allelic variant, adult polyglucosan body disease, a late-onset neurological disorder with a prevalent missense mutation p.Y329S. We have obtained soluble, recombinant GBE1 in wild-type and mutant forms, and determined its 3D crystal structure. Our long-term goal is to establish a molecular basis for disease-causing mutations (e.g. p.Y329S) and develop ‘pharmacological chaperones’ as novel therapeutics.

 Visit the webpage of Adult Polyglucosan Body Disease Research Foundation (APBDRF), where Wyatt Yue contributes as member of its Scientific Advisory Board.

Galactose metabolism, Lenoir pathway, and Galactosemia

Galactose-1-phosphate uridylyltransferase (GALT) is an essential enzyme in the Leloir pathway of galactose metabolism where it reversibly transfers a uridine monophosphate (UMP) group between galactose-1-phosphate and uridine diphosphate glucose, to generate glucose-1-phosphate. Mutations of the GALT gene lead to type I or classical galactosemia, with the most prevalent allele Q188R known to abolish GALT activity completely. We determined the 1.8 Å structure of human GALT ternary complex that contains a covalent uridylylated intermediate and glucose-1-phosphate in the active site. The structure provides a molecular template to understand the role of Gln188, and rationalizes the range of missense mutations associated with type I galactosemia, including Q188R. 

 In summer 2017, we received generous funding support from the Galactosemia Foundation to carry out a fragment screening drug discovery project. 

Read Wyatt Yue's article 'Conference First-timer reflects on Atlanta' on the Galactosemia Foundation newsletter (Winter 2016)

Vitamin B12 and Propionate Metabolism

While Vitamin B­₁₂ serves as the cofactor for only two human enzymes (mitochondrial methylmalonyl-CoA mutase and cytosolic methionine synthase), an intracellular pathway of seven known proteins has evolved for the uptake, processing and delivery of the appropriate cofactor form to the two enzymes. The essentiality of this ‘B₁₂ trafficking pathway’ is underscored by inherited defects reported in all seven proteins, giving rise to the metabolic disorders methylmalonic aciduria and homocystinuria. Despite the well-defined genetic makeup of the B₁₂ pathway, the biochemical function and interplay of the seven proteins, as well as the molecular basis of their genetic defects, remain poorly understood. Since 2010, the Structural Genomics Consortium has adopted a family-based approach in the study of the B₁₂ pathway, with the structure determination of six member proteins (PDB codes: MUT 2XIQ, MMAA 2WWW, MCEE 3RMU, MMACHC 3SOM, MTR 4CCZ, MMADHC 5A4R), resulting in new lessons for the B₁₂ pathway.

• Nicolas Fox (Postdoc 2015-2019), Senior Scientist at Merck Inc
• Minghao Zhang (Research technician 2017-2019), Research Assistant at Target Discovery Institute, Oxford
• Hannah Brazier (DPhil 2013-2017), Medical Writer at Succinct Comms
• Elzbieta Rembeza (Research technician 2015-2017), PhD student in Chalmers University of Technology
• Jola Kopec (Postdoc 2013-2017), Senior Scientist at Evotec
• Stephanie Oerum (DPhil 2012-2016), Postdoc at Université Paris Diderot
• Igor Ferreira (Visiting scientist 2012-2013, Postdoc 2015-2016)
• Thomas McCorvie (SGC postdoc 2012-2015), Research Associate at Imperial College
• Dipali Patel (SGC postdoc 2013-2015), Scientist at Relay Therapeutics
• Izabella Pena (Visiting scientist 2013-2014), Postdoc at MIT
• Fiona Fitzpatrick (Research technician 2013-2015), PhD student at University of Cambridge
• Sean Froese (Postdoc 2010-2013), Assistant Professor at Kinderspital Zurich
• Wasim Kiyani (Research technician 2011-2013), PhD student at Glasgow University
• Naeem Shafqat (Postdoc 2009-2011), Senior Assistant Professor, University Brunei Darussalam
• Ewelina Kryztofinska (Research technician 2009-2011), Scientist at Astex Therapeutics

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