Biology subjects

Kieninger, A.-K.

Publications and source records attributed to Kieninger, A.-K..

4 recordsLinked to original sources

bioRxiv2026

Multi-dimensional optimization of a lysin towards a ribolysin against life-threatening S. aureus infections: Fc-LysM-CHAP and its strong synergy with standard of care antibiotics

Bacterial lysins are promising novel antimicrobials but are limited by poor pharmacokinetics and challenging manufacturability. We developed a lysin discovery platform tailored for lysin delivery via mRNA: staphylococcal LysM-CHAP (cysteine, histidine-dependent amidohydrolases/peptidase) autolysin was selected and its serum half-life extended via Immunoglobulin G1-Fc-fusion. The Fc-induced drop in lysin potency was rescued by the concerted optimization of linkers, binding kinetics and catalytic activity, using a combination of rational and AI-guided approaches. The engineered Fc-LysM-CHAP was active against planktonic bacteria (minimum inhibitory concentration of 1 - 2 {micro}g/mL) and simulated endocardial vegetations and synergized strongly (Fractional eradication concentration index FECI = 0.06) with cell wall active antibiotics in vitro. In mouse models of Staphylococcus aureus sepsis, the recombinant Fc-LysM-CHAP - antibiotic combination was superior to single agent treatments and mRNA-delivered Fc-LysM-CHAP showed single agent activity at a mRNA-lipid nanoparticle dose as low as 0.2 mg/kg.

microbiology↗

bioRxiv2022

SepN is essential for assembly and gating of septal junctions in Nostoc sp. PCC 7120

The multicellular life style of filamentous cyanobacteria like Nostoc sp. PCC7120 relies on a cell-cell communication system involving so called septal junctions. These are multiprotein complexes, which traverse the septal peptidoglycan through nanopores, connecting the neighboring cells and enabling molecule transfer along the filament. The intercellular communication is crucial when different cell types in the filament, vegetative cells and heterocysts, have to exchange metabolites and signaling molecules. Septal junctions of cyanobacteria can even control the molecule exchange by gating. The multiprotein complex consists of three modules: the septum spanning tube, the plug residing within the cytoplasmic membrane at both ends of the tube and a membrane associated cap module, covering the plug/tube modules on the cytoplasmic side of each neighboring cell. Until now, FraD was the only identified protein component of the septal junction protein complexes and localizes to the plug module. Here, we identified SepN as a new component via co-immunoprecipitation using FraD as bait and further demonstrated its essential role in septal junction assembly. Despite normal septal nanopore formation, a mutant in sepN exhibited a highly reduced rate of intercellular communication and was unable to gate the exchange of molecules. Cryo-electron tomography of cryo-focused ion beam thinned sepN-mutant filaments revealed septal junctions lacking the plug module and lateral cap openings. The combination of missing plug but present cap allowed to deduce the importance of the plug module in ensuring the correct cap architecture and, more importantly, in sealing the diffusion area in the closed septal junction state.

microbiology↗

bioRxiv2019

A cytoskeletal network maintains filament shape in the multicellular cyanobacterium Anabaena sp. PCC 7120

Polymerizing and filament-forming proteins are instrumental for numerous cellular processes such as cell division and growth. Their function in stabilization and localization of protein complexes and replicons is achieved by a filamentous structure. Known filamentous proteins assemble into homopolymers consisting of single subunits - e.g. MreB and FtsZ in bacteria - or heteropolymers that are composed of two subunits, e.g. keratin and /{beta} tubulin in eukaryotes. Here, we describe two novel coiled-coil-rich proteins (CCRPs) in the filament forming cyanobacterium Anabaena sp. PCC 7120 (hereafter Anabaena) that assemble into a heteropolymer and function in the maintenance of the Anabaena multicellular shape (termed trichome). The two CCRPs - Alr4504 and Alr4505 (named ZicK and ZacK) - are strictly interdependent for the assembly of protein filaments in vivo and polymerize nucleotide-independently in vitro, similar to known intermediate filament (IF) proteins. A {Delta}zicK{Delta}zacK double mutant is characterized by a zigzagged cell arrangement and hence a loss of the typical linear Anabaena trichome shape. ZicK and ZacK interact with themselves, with each other, with the elongasome protein MreB, the septal junction protein SepJ and the divisome associate septal protein SepI. Our results suggest that ZicK and ZacK function in cooperation with SepJ and MreB to stabilize the Anabaena trichome and are likely essential for the manifestation of the multicellular shape in Anabaena. Our study reveals the presence of filament-forming IF-like proteins whose function is achieved through the formation of heteropolymers in cyanobacteria.

microbiology↗

bioRxiv2018

Structure and function of a bacterial gap junction analog

Multicellular lifestyle requires cell-cell connections. In multicellular cyanobacteria, septal junctions enable molecular exchange between sister cells and are required for cellular differentiation. The structure of septal junctions is poorly understood and it is unknown whether they regulate intercellular communication.\n\nHere we resolved the in situ architecture of septal junctions by electron cryotomography of cryo-focused ion beam-milled cyanobacteria. Septal junctions consisted of a tube traversing the septal peptidoglycan. Each tube end comprised a plug that was covered by a cytoplasmic cap. Fluorescence recovery after photobleaching showed that intercellular communication was blocked upon stress. This gating was accompanied by a conformational change of the septal junctions, mediated by the proteins FraC/D.\n\nWe provide the mechanistic framework for a cell junction that predates eukaryotic gap junctions by a billion years. The conservation of a gated dynamic mechanism across different domains of life emphasizes the importance of controlling molecular exchange, e.g. upon injury.

cell biology↗