Biology subjects

Miggiano, R.

Publications and source records attributed to Miggiano, R..

3 recordsLinked to original sources

bioRxiv2024

DnaB and DciA: Mechanisms of Helicase Loading and Translocation on ssDNA

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=83 SRC="FIGDIR/small/622779v2_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@b0641dorg.highwire.dtl.DTLVardef@7caf59org.highwire.dtl.DTLVardef@1dc0fccorg.highwire.dtl.DTLVardef@913ce2_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO The Vibrio cholerae (Vc) DnaB replicative helicase structure bound to single-stranded (ss) DNA is depicted in the ribbon (top left) and sphere-cylinder representation (top right). In the bottom center is a native mass spectrum showing Vc DnaB helicase loading onto single-stranded DNA (ssDNA). C_FIG Replicative helicases are assembled on chromosomes by helicase loaders before initiation of DNA replication. Here, we investigate mechanisms used by the bacterial Vibrio cholerae (Vc) DnaB replicative helicase and the DciA helicase loader. Structural analysis of the ATP{gamma}S form of the VcDnaB-ssDNA complex reveals a configuration distinct from that seen with GDP*AlF4. With ATP{gamma}S, the amino-terminal (NTD) tier, previously found as an open spiral in the GDP*AlF4 complex, adopts a closed planar arrangement. Further, the DnaB subunit at the top of the carboxy-terminal spiral (CTD) tier is displaced by [~]25 [A] between the two forms. We suggest that remodeling the NTD layer between closed planar and open spiral configurations and migration of two distinct CTDs to the top of the DnaB spiral, repeated three times, mediates hand-over-hand translocation. Biochemical analysis suggests that VcDciA leverages its Lasso domain to contact DnaB near its Docking-Linker-Helix interface. Up to three copies of VcDciA bind to VcDnaB and suppress its ATPase activity during loading onto physiological DNA substrates. Our data suggest that DciA loads DnaB onto DNA using the ring-opening mechanism.

biochemistry↗

bioRxiv2024

ER-mitochondria distance is a critical parameter for efficient mitochondrial Ca2+ uptake and oxidative metabolism.

IP3 receptor (IP3R)-mediated Ca2+ transfer at the mitochondria-endoplasmic reticulum (ER) contact sites (MERCS) drives mitochondrial Ca2+ uptake and oxidative metabolism and is linked to different pathologies, including Parkinsons disease (PD). The dependence of Ca2+ transfer efficiency on the ER-mitochondria distance remains unexplored. Employing molecular rulers that stabilize ER-mitochondrial distances at 5 nm resolution, and using genetically-encoded Ca2+ indicators targeting the ER lumen and the sub-mitochondrial compartments, we now show that a distance of [~]20 nm is optimal for Ca2+ transfer and mitochondrial oxidative metabolism due to enrichment of IP3R at MERCS. In human iPSC-derived astrocytes from PD patients, 20 nm MERCS were specifically reduced which correlated with a reduction of mitochondrial Ca2+ uptake. Our work determines with precision the optimal distance for Ca2+ flux between ER and mitochondria and suggests a new paradigm for fine control over mitochondrial function.

cell biology↗

bioRxiv2023

Endolysin B: A new archetype in M. tuberculosis treatment

So far it is thanks to antibiotics that illnesses, such as Tuberculosis (TB), are treatable. However, antimicrobial misuse combined with Mycobacterium tuberculosis phenotypic plasticity are nullifying the effects of the existing therapies. As a result, increasingly people are dying (one person dies of TB every 20 seconds), especially due to the rise of multi-and extensively drug-resistant strains. There is indeed a urgent need for new and more effective therapies, which should match the requirement of avoiding the rise in drug resistance. Among them, the use of bacteriophage - bacteria-restricted viruses - or simply phage lytic enzyme (i.e., endolysin) represents one of the most promising alternatives. All phages encode for the endolysin A (LysA), which degrades the bacteria cell wall, finally leading to the release of the newly synthesized virions. Nevertheless, mycobacteriophages (bacterial viruses selectively infecting mycobacteria), evolved the additional endolysin B (LysB) to selectively damage the complex mycobacteria cell wall, and to evade from their host. LysB, owing a lipolytic enzyme, can degrade the thick mycolic acid layer, and hence disrupt the integrity of the mycobacterial membrane. Despite its key role in mediating mycobacteria lysis, the molecular mechanism regulating LysB binding to its target remains poorly characterized. Herein, we selected Ms6LysB and created a fluorescent engineered version as a proxy to analyze LysB binding qualitatively and quantitatively to both the fast-growing non-pathogenic Mycobacterium smegmatis and the slow-growing pathogenic M. tuberculosis. Additionally, we shed light on LysB antimicrobial activity upon M. tuberculosis infection, by using alveolar-like mouse macrophages (mAMs) as a cellular model that closely recapitulates the natural niche of M. tuberculosis infection. Our study provides the proof-of-principle that Ms6 LysB binding to the outer mycobacterial membrane can impair M. tuberculosis growth homeostasis and that LysB retain its lytic properties even when internalized by mAMs. This lays the groundwork for the use of LysB as a new therapeutic strategy to undermine M. tuberculosis infection.

microbiology↗