Medical Biology - Research Publications

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End date: 2023 × Start date: 2020 × Type: Preprint ×

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    Defining the molecular architecture, metal dependence, and distribution of metal-dependent class II sulfofructose-1-phosphate aldolases
    Sharma, M ; Kaur, A ; Madiedo Soler, N ; Lingford, J ; Epa, R ; Goddard-Borger, E ; Davies, G ; Williams, S ( 2023-08-08)
    Sulfoquinovose (SQ or 6-deoxy-6-sulfoglucose) is a sulfosugar that is the anionic head group of plant and cyanobacterial sulfolipids: sulfoquinovosyl diacylglycerols. SQ is produced within photosynthetic tissues, forms a major terrestrial reservoir of biosulfur, and is an important species within the biogeochemical sulfur cycle. A major pathway for the breakdown of SQ is the sulfoglycolytic Embden-Meyerhof-Parnas (sulfo-EMP) pathway, which involves cleavage of the 6-carbon chain of the intermediate sulfofructose-1-phosphate (SFP) into dihydroxyacetone and sulfolactaldehyde, catalyzed by class I or II SFP aldolases. While the molecular basis of catalysis is well studied for class I SFP aldolases, comparatively little is known about class II SFP aldolases. Here, we report the molecular architecture and biochemical basis of catalysis of two metal-dependent class II SFP aldolases from Hafnia paralvei and Yersinia aldovae. 3D X-ray structures in complex with the substrate SFP and product DHAP reveal a dimer-of-dimers (tetrameric) assembly, and identify the sulfonate binding pocket that defines the substrate specificity of these enzymes, two metal binding sites, and flexible loops that are implicated in catalysis. Both enzymes were metal dependent and exhibited high KM values for SFP, consistent with their role in a unidirectional nutrient acquisition pathway. Bioinformatic analysis identified a range of sulfo-EMP gene clusters containing class I/II SFP aldolases. The class I and II SFP aldolases occur exclusively within Actinobacteria and Firmicutes phyla, respectively, while both classes of enzyme occur within Proteobacteria. This work emphasizes the importance of SQ as a nutrient for diverse bacterial phyla and the different chemical strategies they use to harvest carbon from this sulfosugar.
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    Trabid patient mutations impede the axonal trafficking of adenomatous polyposis coli to disrupt neurite growth
    Frank, D ; Bergamasco, M ; Mlodzianoski, M ; Kueh, A ; Tsui, E ; Hall, C ; Kastrappis, G ; Voss, AK ; McLean, C ; Faux, M ; Rogers, K ; Tran, B ; Vincan, E ; Komander, D ; Dewson, G ; Tran, H ( 2023-07-19)
    Abstract Trabid/ZRANB1missense mutations have been identified in children diagnosed with a range of congenital disorders including reduced brain size, but how Trabid regulates neurodevelopment is not understood. We have characterised these patient mutations in cells and mice to identify a key role for Trabid in the regulation of neurite growth. One of the patient mutations flanked the catalytic cysteine of Trabid and its deubiquitylating (DUB) activity was abrogated. The second variant retained DUB activity, but failed to bind STRIPAK, a large multiprotein assembly implicated in cytoskeleton organisation and neural development.Trabid/ZRANB1knock-in mice harbouring either of these patient mutations exhibited reduced neuronal and glial cell densities in the brain and a motor deficit consistent with fewer dopaminergic neurons and projections. Mechanistically, both DUB-impaired and STRIPAK-binding-deficient Trabid variants impeded the trafficking of adenomatous polyposis coli (APC) to microtubule plus-ends. Consequently, the formation of neuronal growth cones and the trajectory of neurite outgrowth from mutant midbrain progenitors were severely compromised. We propose that STRIPAK recruits Trabid to deubiquitylate APC, and that in cells with mutant Trabid, APC becomes hyperubiquitylated and mislocalised causing impaired organisation of the cytoskeleton that underlie the neuronal and developmental phenotypes.