The discovery of antibiotics in the 20th century was one of the most significant advances in global health. Since their introduction, antibiotics have saved millions of lives from bacterial infections and extended the average human lifespan by more than two decades. However, widespread overuse and misuse have driven the emergence of antimicrobial resistance (AMR). Today, the WHO recognises AMR as one of the most urgent threats to global public health and food security. A major driver of AMR is the horizontal spread of antibiotic resistance genes carried on plasmids. These extrachromosomal DNA elements can move between cells, and even across species, via a process known as conjugation. This highly efficient mode of gene transfer underpins the rapid global dissemination of resistance traits among pathogenic bacteria. Examples of long-range gene regulation in bacteria are rare and generally thought to involve DNA looping. We used a combination of X-ray crystallography, biophysics and single-molecule analysis to investigate the KorB-KorA system in Escherichia coli. We show that long-range gene silencing on the plasmid RK2, a source of multi-drug resistance across diverse Gram-negative bacteria, is achieved cooperatively by the DNA-sliding clamp protein KorB, and the clamp-locking protein KorA. We show that KorB is a CTPase clamp that can entrap and slide along DNA to reach distal target promoters up to 1.5 kb away. We resolved the tripartite crystal structure of a KorB-KorA-DNA co-complex, revealing that KorA latches KorB into a closed clamp state. DNA-bound KorA thus stimulates repression by stalling KorB sliding at target promoters to occlude RNA polymerase holoenzymes. Together, our findings explain the mechanistic basis for KorB role switching from a DNA-sliding clamp to a co-repressor and provide an alternative mechanism for long-range regulation of gene expression in bacteria. By uncovering the structural and mechanistic basis of plasmid gene silencing by the KorBKorA system, our work provides new insight into how resistance genes are regulated on broad-host-range plasmids. Understanding this novel mode of long-range gene repression deepens our knowledge of plasmid biology and highlights potential strategies for controlling the spread and expression of antibiotic resistance determinants.