Biology subjects

Elmlund, H.

Publications and source records attributed to Elmlund, H..

3 recordsLinked to original sources

bioRxiv2026

An expanded LPS translocon mediates surface lipoprotein export in the Bacteroidota

Cell surface lipoproteins (SLPs) play crucial roles in the pathogenesis and cell biology of gram-negative bacteria, yet the route by which they reach the cell surface has remained unknown except in special cases. Here we show that in Bacteroidota bacteria, a phylum that includes prominent human commensals and anaerobic pathogens, SLP export is carried out by the outer membrane lipopolysaccharide (LPS) translocon. Isolation and structural characterisation of LPS translocon complexes from two Bacteroidota species reveals that they are massively enlarged and elaborated relative to the Escherichia coli paradigm with up to eight additional subunits located within, and on either side of, the outer membrane. We establish a role for the universally conserved core LptD subunit and four of the additional Bacteroidota-specific subunits in SLP export. Expansion of the LPS translocon in the Bacteroidota may allow export of the unusually complex SLPs found in this phylum. Our discoveries raise the possibility that SLP export is a conserved second function of the LPS transport pathway across gram-negative bacteria.

microbiology↗

bioRxiv2020

Structural analysis of the PTEN:P-Rex2 signalling node reveals how cancer-associated mutations coordinate to hyperactivate Rac1

The PTEN:P-Rex2 complex is one of the most commonly mutated signaling nodes in metastatic cancer. Assembly of the PTEN:P-Rex2 complex inhibits the activity of both proteins, and its dysregulation can drive PI3K-AKT signaling and cell proliferation. Here, using extensive crosslinking mass spectrometry and functional studies, we provide crucial mechanistic insights into PTEN:P-Rex2 complex assembly and co-inhibition. PTEN is anchored to P-Rex2 by interactions between the PTEN PDZ-BM tail and the second PDZ domain of P-Rex2. This interaction bridges PTEN across the P-Rex2 surface, occluding PTEN membrane-binding and PI(3,4,5)P3 hydrolysis. Conversely, PTEN both allosterically promotes an autoinhibited P-Rex2 conformation and occludes G{beta}{gamma} binding and GPCR activation. These insights allow us to define a new gain-of-function class of cancer mutations within the PTEN:P-Rex2 interface that uncouples PTEN inhibition of Rac1 signaling. These findings provide a mechanistic framework to understand the dysregulation of the PTEN:P-Rex2 signaling node in metastatic cancer.

biochemistry↗

bioRxiv2019

AgarFix: simple and accessible stabilization of challenging single-particle cryo-EM specimens through cross-linking in a matrix of agar

Cryogenic electron microscopy (cryo-EM) allows structure determination of macromolecular assemblies that have resisted other structural biology approaches because of their size and heterogeneity. These challenging multi-protein targets are typically susceptible to dissociation and/or denaturation upon cryo-EM grid preparation, and often require cross-linking prior to freezing. Several approaches for gentle on-column or in-tube crosslinking have been developed. On-column cross-linking is not widely applicable because of the poor separation properties of gel filtration techniques. In-tube crosslinking frequently causes sample aggregation and/or precipitation. Gradient-based cross-linking through the GraFix method is more robust, but very time-consuming and necessitates specialised expensive equipment. Furthermore, removal of the glycerol typically involves significant sample loss and may cause destabilization detrimental to the sample quality. Here, we introduce an alternative procedure: AgarFix (Agarose Fixation). The sample is embedded in an agarose matrix that keeps the molecules separated, thus preventing formation of aggregates upon cross-linking. Gentle cross-linking is accomplished by diffusion of the cross-linker into the agarose drop. The sample is recovered by diffusion or electroelution and can readily be used for cryo-EM specimen preparation. AgarFix requires minimal equipment and basic lab experience, making it widely accessible to the cryo-EM community.\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=70 SRC=\"FIGDIR/small/569087_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (15K):\norg.highwire.dtl.DTLVardef@72305borg.highwire.dtl.DTLVardef@c4c978org.highwire.dtl.DTLVardef@186f823org.highwire.dtl.DTLVardef@cfd16_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIFragile protein complexes can be cross-linked while embedded in agarose\nC_LIO_LIThe agarose matrix prevents formation of aggregates upon cross-linking\nC_LIO_LICross-linking in agarose is easy, fast, and requires no expensive equipment\nC_LIO_LIThe sample can directly be used for negative stain or cryo-EM grid preparation\nC_LI

biochemistry↗