Biology subjects

Yelland, T.

Publications and source records attributed to Yelland, T..

4 recordsLinked to original sources

bioRxiv2025

Receptor-substrate competition for the TonB homologue FusB suggests a model for ferredoxin import in Pectobacterium spp.

TonB-dependent uptake systems of Gram-negative bacterial pathogens constitute prominent virulence factors, allowing nutrient acquisition, primarily siderophore-bound iron, to cross the highly impermeable outer membrane (OM). Remarkably, the ferredoxin uptake system (Fus) of Pectobacteriaceae, a group of soft rot-inducing plant pathogens, imports an entire folded host protein into the periplasm and extracts its bound iron for growth. The inner membrane protein FusB, a TonB homologue, plays two roles in facilitating ferredoxin import. First, like other TonBs, it remodels the globular plug domain obstructing the lumen of the OM receptor FusA to allow ferredoxin passage. Unusually for a TonB protein, FusB then interacts directly with the FusA-bound ferredoxin substrate to facilitate its transport into the periplasm. In this work, we describe structures of FusB-ferredoxin and homodimeric FusB complexes and determine the key features of the binding interfaces formed by FusB with FusA and ferredoxin. We postulate that under resting conditions FusB exists a homodimer, stabilised by an intermolecular R241-D322 salt bridge. The homodimer dissociates when the "FusB-box" of FusA outcompetes one protomer, and FusA D53 displaces FusB D322. Upon ferredoxin binding, FusB undergoes a structural rearrangement, expanding its {beta}-sheet from three to four strands. In agreement with the proposed sequence of events, ferredoxin binding displaces the receptor (FusA) from FusB with Arg241 forming an intramolecular salt bridge with Asp322 to stabilise the newly formed {beta}-hairpin of FusB. We propose a mechanistic model for ferredoxin import in which FusB Arg241 acts as a molecular switch, and two distinct regions function as interaction hotspots.

biophysics↗

bioRxiv2024

Structural basis for collagen recognition by the Streptococcus pyogenes M3 protein and its involvement in biofilm

The M protein is an essential virulence factor of Streptococcus pyogenes, or group A streptococcus (GAS), one of the most common and dangerous human pathogens. Molecular and functional characterization of M protein variants and their interactions with host components is crucial for understanding streptococcal pathogenesis and vaccine development. The M3 protein is produced by the prevalent emm3 GAS serotype, which is frequently associated with severe invasive diseases. Here we characterize the interaction of M3 with human collagens through detailed structural and biochemical binding analysis. High-resolution structures of the N-terminal M3 domain in the free state as well as bound to a collagen peptide derived from the Collagen Ligands Collection reveal a novel T-shaped protein fold that presents binding sites complementing the characteristic topology of collagen triple helices. The structure of the M3/collagen peptide complex explains how emm3 GAS and related streptococci, such as the emerging human pathogen Streptococcus dysgalactiae subsp. equisimilis, can target collagens to enable colonization of various tissues. In line with this, we demonstrate that the M3/collagen interaction promotes enhanced biofilm formation of emm3 GAS in an emm type specific manner, which can be inhibited with the recombinant M3 N-terminal domain fragment. Further, emm3 GAS are shown to colocalize with collagen in tissue biopsies from patients with necrotizing soft tissue infections, where GAS biofilms are common. This observation is reproduced in infected organotypic skin models. Together, these data provide detailed molecular insights into an important streptococcal virulence mechanism with implications for the understanding of invasive infections, strategies for treating biofilm and M-protein based vaccine design.

microbiology↗

bioRxiv2020

CYRI-A regulates macropinocytic cup maturation and mediates integrin uptake, limiting invasive migration

The Scar/WAVE complex is the major driver of actin nucleation at the plasma membrane, resulting in lamellipodia and membrane ruffles. While lamellipodia aid migration, membrane ruffles can generate macropinosomes - cup-like structures - important for nutrient uptake and regulation of cell surface receptor levels. How macropinosomes are formed and the role of the actin machinery in their formation and resolution is still not well understood. Mammalian CYRI-B is a recently described negative regulator of the Scar/WAVE complex by RAC1 sequestration, but its other paralogue, CYRI-A has not been characterised. Here we implicate CYRI-A as a key regulator of macropinosome maturation and integrin internalisation from the cell surface. We find that CYRI-A is recruited to nascent macropinosomes in a transient but distinct burst, downstream of PIP3-mediated RAC1 activation and the initial burst of actin assembly driving cup formation, but upstream of internalisation and RAB5 recruitment to the macropinosome. Together, our data place CYRI-A as a local suppressor of actin dynamics, enabling the resolution of the macropinocytic cup. The failure of CYRI-depleted cells to resolve their macropinocytic cups results in reduced integrin a5b1 internalisation, leading to enhanced spreading, invasive behaviour and anchorage-independent 3D growth. We thus describe a new role for CYRI-A as a highly dynamic regulator of RAC1 activity at macropinosomes, modulating homeostasis of integrin surface presentation, with important functional consequences.

cell biology↗

bioRxiv2019

Spatial restriction of phosphoinositide metabolism is a molecular switch to promote metastasis.

The signalling pathways underpinning cell growth and invasion use overlapping components, yet how mutually exclusive cellular responses occur is unclear. We developed 3-Dimensional culture analyses to separately quantify growth and invasion. We identify that alternate variants of IQSEC1, an ARF GTPase Exchange Factor, act as switches to promote invasion over growth by spatially enriching cortical phosphoinositide metabolism. All IQSEC1 variants activate ARF5- and ARF6-dependent PIP5-kinase to promote PI(3,4,5)P3-AKT signalling and growth. In contrast, select pro-invasive IQSEC1 variants restrict PI(3,4,5)P3 production to discrete cortical domains to form invasion-driving protrusions. Inhibition of IQSEC1 attenuates invasion in vitro and metastasis in vivo. Induction of pro-invasive IQSEC1 variants and elevated IQSEC1 expression occurs in a number of tumour types and is associated with higher-grade metastatic cancer, activation of PIP3-signalling, and predicts long-term poor outcome across multiple cancers. Spatial enrichment of phosphoinositide metabolism therefore is a switch to induce invasion over growth in response to the same external signal. Targeting IQSEC1 as the central regulator of this switch may represent a therapeutic vulnerability to stop metastasis. HighlightsO_LISpatial enrichment of PI(3,4,5)P3 is a molecular switch to promote invasion. C_LIO_LIIQSEC1 is a GEF for ARF5/6, promoting PIP5K-dependent PI(3,4,5)P3 production downstream of the HGF receptor Met. C_LIO_LIPro-invasive IQSEC1 variants restrict cortical PI(3,4,5)P3 production to subdomains that convert into invasive protrusions. C_LIO_LIIQSEC1 inhibition attenuates in vitro invasion and metastasis in vivo. C_LIO_LIIQSEC1 module is associated with poor outcome across tumour types. C_LI

cancer biology↗