Biology subjects

Treuner-Lange, A.

Publications and source records attributed to Treuner-Lange, A..

4 recordsLinked to original sources

bioRxiv2026

Discovery of PilU as a second Type IV pilus retraction motor in Myxococcus xanthus

Type IV pili (T4P) drive social (S) motility in Myxococcus xanthus through cycles of extension and retraction powered by the ATPases PilB and PilT. Although the canonical retraction ATPase PilT is essential for force generation, M. xanthus encodes four PilT-like paralogs whose contributions to motility remain unclear. Here, we identify MXAN_1995 as the long-sought PilU protein that serves as a second T4P retraction motor. A frameshift mutation or deletion of pilU abolishes S-motility, while preserving pilus assembly and exopolysaccharide (EPS) production, phenocoping the pilT mutant. Single-cell analyses revealed that {Delta}pilU mutants exhibit rare, low-force movements, consistent with a role for PilU in force generation. Fluorescence microscopy showed PilU localizes predominantly to cell poles, similar to PilT; this localization is independent of PilT but partially dependent on core T4P assembly proteins. Notably, calcium differentially modulates motility, enhancing movement in wild-type cells while suppressing it in {Delta}pilU mutants, indicating a role for PilU under varying environmental conditions. Structural modeling, together with an intragenic suppressor, highlights a regulatory function for the intrinsically disordered C-terminal region of PilU. Together, our findings establish PilU as a secondary retraction ATPase and uncover a dual-motor retraction system that is environmentally responsive and mechanically tunable. ImportanceT4P are widespread motility and adhesion systems that enable bacteria to move, interact, and form multicellular communities. While the primary retraction ATPase PilT is well characterized, the function of additional PilT-like proteins remains unclear in many species. This work provides the first mechanistic characterization of PilU in Myxococcus xanthus, a model for multicellular behavior and T4P biology. We show that PilU is essential for productive T4P retraction, functioning as an accessory motor that enhances or stabilizes PilT-driven force generation. We further reveal that PilU activity is modulated by environmental calcium and depends on a flexible C-terminal region that influences motor complex dynamics. These findings uncover a dual-motor architecture that enables adaptive control of T4P retraction in response to environmental cues.

microbiology↗

bioRxiv2024

Combinatorial control of type IVa pili formation by the four polarized regulators MglA, SgmX, FrzS and SopA

Type IVa pili (T4aP) are widespread and enable bacteria to translocate across surfaces. T4aP engage in cycles of extension, surface adhesion and retraction, thereby pulling cells forward. Accordingly, the number and localization of T4aP are critical to efficient translocation. Here, we address how T4aP formation is regulated in Myxococcus xanthus, which translocates with a well-defined leading and lagging cell pole using T4aP at the leading pole. This localization is orchestrated by the small GTPase MglA and its downstream effector SgmX that both localize at the leading pole and recruit the PilB extension ATPase to the T4aP machinery at this pole. Here, we identify the previously uncharacterized protein SopA and show that it interacts directly with SgmX, localizes at the leading pole, stimulates polar localization of PilB, and is important for T4aP formation. We corroborate that MglA also recruits FrzS to the leading pole, and that FrzS stimulates SgmX recruitment. In addition, FrzS and SgmX separately recruit SopA. Precise quantification of T4aP formation and T4aP-dependent motility in various mutants support a model whereby the main pathway for stimulating T4aP formation is the MglA/SgmX pathway. FrzS stimulates this pathway by recruiting SgmX and SopA. SopA stimulates the MglA/SgmX pathway by stimulating the function of SgmX, likely by promoting the SgmX-dependent recruitment of PilB. The architecture of the MglA/SgmX/FrzS/SopA protein interaction network for orchestrating T4aP formation allows for combinatorial regulation of T4aP levels at the leading cell pole resulting in discrete levels of T4aP-dependent motility.

microbiology↗

bioRxiv2023

Large pilin subunits provide distinct structural and mechanical properties for the Myxococcus xanthus type IV pilus

Type IV pili (T4P) are ubiquitous bacterial cell surface filaments important for surface motility, adhesion to biotic and abiotic surfaces, DNA uptake, biofilm formation, and virulence. T4P are built from thousands of copies of the major pilin subunit and tipped by a complex composed of minor pilins and in some systems also the PilY1 adhesin. While the major pilins of structurally characterized T4P have lengths of up to 161 residues, the major pilin PilA of Myxococcus xanthus is unusually large with 208 residues. All major pilins have a highly conserved N-terminal domain and a highly variable C-terminal domain, and the additional residues in the M. xanthus PilA are due to a larger C-terminal domain. We solved the structure of the M. xanthus T4P (T4PMx) at a resolution of 3.0 [A] using cryo-electron microscopy (cryo-EM). The T4PMx follows the structural blueprint observed in other T4P with the pilus core comprised of the extensively interacting N-terminal 1-helices while the globular domains decorate the T4P surface. The atomic model of PilA built into this map shows that the large C-terminal domain has much more extensive intersubunit contacts than major pilins in other T4P. As expected from these greater contacts, the bending and axial stiffness of the T4PMx is significantly higher than that of other T4P and supports T4P-dependent motility on surfaces of different stiffnesses. Notably, T4PMx variants with interrupted intersubunit interfaces had decreased bending stiffness and strongly reduced motility on all surfaces. These observations support an evolutionary scenario whereby the large major pilin enables the formation of a rigid T4P that expands the environmental conditions in which the T4P system functions.

microbiology↗

bioRxiv2021

A repurposed, non-canonical cytochrome c, chaperones calcium binding by PilY1 for type IVa pili formation

Type IVa pili (T4aP) are versatile bacterial cell surface structures that undergo extension/adhesion/retraction cycles powered by the cell envelope-spanning T4aP machine. In this machine, a complex composed of four minor pilins and PilY1 primes T4aP extension and is also present at the pilus tip mediating adhesion. Similar to many other bacteria, Myxococcus xanthus contains multiple minor pilins/PilY1 sets that are incompletely understood. Here, we report that minor pilins and PilY1 (PilY1.1) of cluster_1 form priming and tip complexes contingent on a non-canonical cytochrome c (TfcP) with an unusual His/Cys heme ligation and calcium. We provide evidence that TfcP is unlikely to participate in electron transport and has been repurposed to promote calcium binding by PilY1.1 at low calcium concentrations, thereby stabilising PilY1.1 and enabling T4aP function in a broader range of calcium concentrations. These results identify a novel function of cytochromes c and illustrate how incorporating an accessory factor expands the environmental range under which the T4aP system functions.

microbiology↗