Graduate Students Mini Symposium VII 2025

13:15 h Lena Schmück - AG Schuller

The path of the iron-sulfur clusters into the proteins: Unveiling the sulfur mobilization machinery

Iron-sulfur (FeS) cluster containing proteins are ubiquitous in nature and conserved across all kingdoms of life. However, they are not assembled within their target proteins. Instead, FeS clusters are assembled on scaffold proteins assisted by specialized assembly machinery. The most ancient of the identified FeS cluster biogenesis systems is the Sulfur Mobilization Machinery (SUF). This machinery contains the proteins SufS, SufE or SufU, SufBCD or SufBC, and SufA proteins. It is postulated that the SufBCD/SufBC protein complex assembles FeS clusters on its SufBD subunits. SufC belongs to the highly diverse ABC ATPase-family, whose function within the FeS cluster biogenesis pathway remains unresolved. To overcome this, structures in the enzyme’s conformational cycles are required to understand how the ATPase movement is related to the formation of a nascent FeS cluster. We determined a high-resolution structure of the SufBC protein complex, focusing on the proposed FeS cluster forming residues and the proposed ATPase activity-induced, conformational changes. Our data show that the SufBC complex adopts different structural conformations during FeS cluster assembly.

13:45 h Juri Hanßmann - AG Thanbichler

Beyond ParB: Evolution of the chromosome partitioning protein ParB and discovery of an atypical ParB-like transcriptional regulator

The precise coordination of cellular processes such as cell-cycle regulation is critical for every organism. Therefore, a vast repertoire of regulatory proteins including proteins regulated by small molecules such as nucleotides has evolved. Recent studies on ParB, a protein involved in bacterial DNA segregation, led to the discovery of a novel class of CTP-dependent molecular switches. Importantly, database searches suggested that the ParB/Srx domain of ParB, which mediates its ability to bind and hydrolyze CTP, may be widely conserved among bacteria and archaea. In this study, we combined bioinformatic and biochemical approaches to identify novel nucleotide-regulated proteins and found an ATP-dependent atypical transcriptional regulator involved in the activation of E. coli adhesins.

Apart from that, we used ancestral sequence reconstruction and biochemical studies to unravel the evolution of ParB-type DNA segregation proteins. We show that ParB is an ancient protein whose core functions were preserved over billions of years of evolution. Collectively, this work highlights the prevalence and importance of ParB/Srx-type NTPases in bacteria, thereby shedding light on a widespread new mode of regulation in bacteria.