Biology subjects

Klusch, N.

Publications and source records attributed to Klusch, N..

3 recordsLinked to original sources

bioRxiv2026

A bifunctional RNase H protein supports DNA replication and transcription in nucleus-forming Chimalliviridae phages

Jumbo bacteriophages of the Chimalliviridae family replicate their genomes within a proteinaceous phage nucleus that spatially segregates viral DNA replication and transcription from translation. While the phage nucleus protects viral DNA from host defenses, it also imposes unique constraints on genome replication and gene expression. Here we identify the phage-encoded protein Rhc (RNase H-clamp) as a central mediator of genome transactions within the phage nucleus. Using the Escherichia coli infecting bacteriophage Goslar, we show that Rhc functions as an essential component of a non-canonical three-subunit DNA polymerase complex composed of DNAPN, DNAPC and Rhc. Rhc physically interacts with the DNAPC subunit, and both the catalytic activity of Rhc's N-terminal RNase H domain and its C-terminal sliding clamp-derived DNA binding domain are required for genome replication, nuclear maturation, and productive infection. Further, Goslar Rhc also supports transcription within the phage nucleus through a function that is separable from its DNA replication function. Rhc depletion results in reduced transcription of a subset of late genes, in a pattern that suggests a role for Rhc in resolving R-loops. Imaging and cryo-electron tomography reveal that loss of Rhc arrests phage development at a nascent nuclear stage, uncoupling nuclear assembly from maturation. Together, these findings identify Rhc as a multifunctional nuclear factor that mediates both DNA replication and transcription in nucleus-forming jumbo phages, revealing how viruses repurpose a conserved enzymatic activity to coordinate gene expression within a compartmentalized replication environment.

cell biology↗

bioRxiv2020

A ferredoxin bridge connects the two arms of plant mitochondrial complex I

Mitochondrial complex I is the main site for electron transfer to the respiratory chain and generates much of the proton gradient across the inner mitochondrial membrane. It is composed of two arms, which form a conserved L-shape. We report the structures of the intact, 47-subunit mitochondrial complex I from Arabidopsis thaliana and from the green alga Polytomella sp. at 3.2 and 3.3 [A] resolution. In both, a heterotrimeric {gamma}-carbonic anhydrase domain is attached to the membrane arm on the matrix side. Two states are resolved in A. thaliana complex I, with different angles between the two arms and different conformations of the ND1 loop near the quinol binding site. The angle appears to depend on a bridge domain, which links the peripheral arm to the membrane arm and includes an unusual ferredoxin. We suggest that the bridge domain regulates complex I activity. One sentence summaryThe activity of complex I depends on the angel between its two arms, which, in plants, is adjusted by a protein bridge that includes an unusual ferredoxin. The authors responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) are: Hans-Peter Braun (braun@genetik.uni-hannover.de) and Werner Kuhlbrandt (werner.kuehlbrandt@biophys.mpg.de).

plant biology↗

bioRxiv2019

Rotary substates of mitochondrial ATP synthase reveal the basis of flexible F1-Fo coupling

F1Fo-ATP synthases play a central role in cellular metabolism, making the energy of the proton-motive force across a membrane available for a large number of energy-consuming processes. We determined the single-particle cryo-EM structure of active dimeric ATP synthase from mitochondria of Polytomella sp. at 2.7- 2.8 [A] resolution. Separation of 13 well-defined rotary substates by 3D classification provides a detailed picture of the molecular motions that accompany c-ring rotation and result in ATP synthesis. Crucially, the F1 head rotates along with the central stalk and c-ring rotor for the first ~30{degrees} of each 120{degrees} primary rotary step. The joint movement facilitates flexible coupling of the stoichiometrically mismatched F1 and Fo subcomplexes. Flexibility is mediated primarily by the interdomain hinge of the conserved OSCP subunit, a well-established target of physiologically important inhibitors. Our maps provide atomic detail of the c-ring/a-subunit interface in the membrane, where protonation and deprotonation of c-ring cGlu111 drives rotary catalysis. An essential histidine residue in the lumenal proton access channel binds a strong non-peptide density assigned to a metal ion that may facilitate c-ring protonation, as its coordination geometry changes with c-ring rotation. We resolve ordered water molecules in the proton access and release channels and at the gating aArg239 that is critical in all rotary ATPases. We identify the previously unknown ASA10 subunit and present complete de novo atomic models of subunits ASA1-10, which make up the two interlinked peripheral stalks that stabilize the Polytomella ATP synthase dimer.

biochemistry↗