Biology subjects

Mainz, A.

Publications and source records attributed to Mainz, A..

4 recordsLinked to original sources

bioRxiv2026

Molecular mechanism of albicidin-dependent transcription activation by the antibiotic resistance factor AlbA

The escalating spread of antimicrobial resistance demands antibiotics with novel mechanisms of action. Albicidin is a potent DNA gyrase inhibitor produced by Xanthomonas species, and bacteria counter its activity through resistance mechanisms including the albicidin-sequestering protein AlbA from Klebsiella oxytoca. AlbA is a MerR family transcription activator that binds albicidin and stimulates expression of the albA gene, but how ligand recognition is coupled to transcription activation has remained unclear. Here, we use cryogenic electron microscopy and complementary biochemical assays to define the mechanism of AlbA-dependent transcription activation. Structures of transcription complexes reveal that AlbA remodels the promoter, repositioning the -35 element for productive sigma70 recognition and RNA polymerase engagement. Albicidin does not measurably alter AlbAs DNA affinity or the architecture of the mature open complex. Instead, transcription kinetics and experiments bypassing promoter opening indicate that albicidin selectively facilitates a promoter opening-dependent transition. AlbA is released upon synthesis of approximately five nucleotides, concomitant with downstream DNA melting, bubble translocation and upstream DNA rewinding rather than DNA scrunching. Together, these findings establish a sequential mechanism in which AlbA remodels promoter architecture, while albicidin tunes the kinetic transition to promoter opening, linking antibiotic recognition to induction of its sequestration machinery.

biochemistry↗

bioRxiv2026

An Oligomeric Lanthipeptide from Nostoc punctiforme Promotes Host Association During Early Symbiosis with Blasia pusilla

Nitrogen-fixing Nostoc species form symbiotic relationships with diverse plants, yet the role of specialized metabolites in these interactions remains poorly understood. Here, we identify a previously cryptic gene cluster coding for the biosynthesis of the lanthipeptide nostolanthin (nlt), which is rapidly induced upon physical contact between Nostoc punctiforme and the liverwort Blasia pusilla. Despite its robust transcriptional activation, nostolanthin remained undetectable in its native producer by conventional metabolomic analyses. Heterologous reconstitution of the biosynthesis showed that the lanthipeptide synthetase NltM produces a bicyclic class II lanthipeptide containing a non-cyclized dehydroamino acid together with a free cysteine residue. We show that this lanthipeptide undergoes covalent oligomerization into high-molecular-weight assemblies, a process favored under native cyanobacterial expression conditions. An antibody raised against the oligomeric peptide enabled the detection of secreted nostolanthin in cyanobacteria and revealed that it accumulates predominantly in an oligomeric form. Comparative genomics showed that nostolanthin belongs to a larger family of Nif11-type-lanthipeptide biosynthetic gene clusters, consistently associated with homologous two-component regulatory systems. Importantly, oligomeric, but not monomeric nostolanthin, accelerated the establishment of physical contact between Nostoc and B. pusilla. Together, these findings reveal oligomerization by covalent bond formation as a previously unrecognized mode of lanthipeptide maturation and identify nostolanthin as a host-responsive peptide that regulates the transition from a free-living to a symbiotic lifestyle.

microbiology↗

bioRxiv2024

Paenilamicins from the honey bee pathogen Paenibacillus larvae are context-specific translocation inhibitors of protein synthesis

The paenilamicins are a group of hybrid non-ribosomal peptide-polyketide compounds produced by the honey bee pathogen Paenibacillus larvae that display activity against Gram-positive pathogens, such as Staphylococcus aureus. While paenilamicins have been shown to inhibit protein synthesis, their mechanism of action has remained unclear. Here, we have determined structures of the paenilamicin PamB2 stalled ribosomes, revealing a unique binding site on the small 30S subunit located between the A- and P-site tRNAs. In addition to providing a precise description of interactions of PamB2 with the ribosome, the structures also rationalize the resistance mechanisms utilized by P. larvae. We could further demonstrate that PamB2 interferes with the translocation of mRNA and tRNAs through the ribosome during translation elongation, and that this inhibitory activity is influenced by the presence of modifications at position 37 of the A-site tRNA. Collectively, our study defines the paenilamicins as a new class of context-specific translocation inhibitors.

biochemistry↗

bioRxiv2021

Molecular Basis of Antibiotic Self-Resistance in a Bee Larvae Pathogen

Paenibacillus larvae, the causative agent of the devastating honey-bee disease American Foulbrood, produces the cationic polyketide-peptide hybrid paenilamicin that displays high antibacterial and antifungal activity. Its biosynthetic gene cluster contains a gene coding for the N-acetyltransferase PamZ. We show that PamZ acts as self-resistance factor in P. larvae by deactivation of paenilamicin. Using tandem MS, NMR spectroscopy and synthetic diastereomers, we identified the N-terminal amino group of the agmatinamic acid as the N-acetylation site. These findings highlight the pharmacophore region of paenilamicin, which we very recently identified as a new ribosome inhibitor. Here, we further elucidated the crystal structure of PamZ:acetyl-CoA complex at 1.34 [A] resolution. An unusual tandem-domain architecture provides a well-defined substrate-binding groove decorated with negatively-charged residues to specifically attract the cationic paenilamicin. Our results will help to understand the mode of action of paenilamicin and its role in pathogenicity of P. larvae to fight American Foulbrood.

biochemistry↗