Biology subjects

Mc Guinness, C.

Publications and source records attributed to Mc Guinness, C..

3 recordsLinked to original sources

bioRxiv2025

The host protein cyclophilin A inhibits HIV-1 nuclear entry by decreasing capsid elasticity

Binding of the host protein cyclophilin A (CypA) to the HIV-1 capsid exerts a variety of effects on infection, including enhancement of reverse transcription, stabilization of the capsid, and promotion of nuclear entry. For several HIV-1 mutants, CypA binding inhibits nuclear entry by an unknown mechanism. We recently demonstrated that HIV-1 cores are elastic and that HIV-1 mutants with inelastic capsids are impaired for nuclear entry and infection of nondividing cells. Here we show that CypA prevents infection of nondividing cells by such mutants and inhibits their entry into the nucleus. CypA binding to mutant cores further reduced their elasticity in vitro, and this effect was reversed by suppressor mutations that restored nuclear entry. We suggest that HIV-1 nuclear entry involves temporal modulation of capsid elasticity by host proteins prior to and during traversal of the nuclear pore.

microbiology↗

bioRxiv2024

Development of a generalisable tryptophan-optimised quenchbody biosensor based on a synthetic nanobody library

Quenchbodies, antibodies labelled with fluorophores that increase in intensity upon antigen binding, offer great promise for biosensor development. Nanobody-based quenchbodies are particularly attractive due to their small size, ease of expression, high stability, rapid evolvability, and amenability to protein engineering. However, existing designs for protein detection show limited dynamic range, with fluorescence increases of only 1.1-1.7 fold. Here we identify the tryptophan residues in the nanobody complementarity-determining regions (CDRs) that are critical to quenchbody performance. Using a combination of rational design and molecular dynamics simulations, we developed an optimised nanobody scaffold with tryptophans introduced at key positions. We used this scaffold in an in vitro directed-evolution screen against human inflammatory cytokine interleukin-6 (IL-6). This yielded quenchbodies with 1.5-2.4-fold fluorescence increases, enabling IL-6 detection down to 2 nM. Our scaffold provides a valuable platform for developing biosensors for diverse protein targets, with applications in research, diagnostics, and environmental monitoring.

bioengineering↗

bioRxiv2021

Single-molecule analysis of the entire perfringolysin O poreformation pathway

The cholesterol-dependent cytolysin perfringolysin O (PFO) is secreted by Clostridium perfringens as a bacterial virulence factor able to form giant ring-shaped pores that perforate and ultimately lyse mammalian cell membranes. To resolve the kinetics of all steps in the assembly pathway, we have used single-molecule fluorescence imaging to follow the dynamics of PFO on dye-loaded liposomes that lead to opening of a pore and release of the encapsulated dye. Formation of a long-lived membrane-bound PFO dimer nucleates the growth of an irreversible oligomer. The growing oligomer can insert into the membrane and open a pore at stoichiometries ranging from tetramers to full rings ([~]35-mers), whereby the rate of insertion increases linearly with the number of subunits. Oligomers that insert before the ring is complete continue to grow by monomer addition post insertion. Overall, our observations suggest that PFO membrane insertion is kinetically controlled.

biophysics↗