Leishmania donovani HslV does not interact stably with HslU proteins

The HslVU protease system is present in bacteria and some eukaryotic pathogens. Its role in Leishmania donovani remains unclear. Prior research has shown HslVU is involved in protein degradation. No prior work had resolved whether HslV functions independently in Leishmania. This gap motivated the current investigation. The essentiality of HslV in Leishmania viability was unknown. Previous studies suggested HslV may act with HslU in other organisms. This uncertainty drove the analysis of HslV and HslU interactions in Leishmania.

This study aimed to clarify the role of HslV and HslU in Leishmania donovani. The researchers sought to determine if HslV is essential for viability. They also investigated whether HslU proteins interact with HslV. The motivation was to understand the proteolytic system in this parasite. The lack of HslV in mammals suggests it may be a drug target. The researchers wanted to test if HslV functions alone or with HslU. They also examined if the function is conserved across species. The study focused on the structural and functional properties of HslV.

The researchers replaced all three HslV/HslU gene homologues in Leishmania. They used gene replacement techniques to assess viability. They tested the ability of Leishmania HslV to rescue an E. coli mutant. The E. coli strain lacked HslVU, Lon, and ClpXP proteases. They performed co-immunoprecipitation to check for HslV-HslU interactions. They analyzed the subcellular distribution of HslV. They used electron microscopy to study the complex structure. The team compared the results to known bacterial HslVU systems.

HslV was found to be essential for Leishmania donovani survival. The Leishmania HslV partially rescued an E. coli protease mutant. This suggests a conserved proteolytic function across species. HslV formed a dodecameric complex without HslU. The complex showed a punctate distribution in cells. Neither HslU gene in Leishmania interacted stably with HslV. Co-immunoprecipitation failed to show a stable complex. The results indicate HslV functions independently in this parasite.

The basic function of HslV may be conserved in Leishmania. However, the interaction with HslU is not present in this species. The researchers propose that HslV forms a distinct complex. The absence of HslU interaction suggests functional divergence. The dodecameric structure supports this idea. The essential role of HslV in Leishmania viability is clear. Since HslV is not found in mammals, it is a potential drug target. The findings suggest a unique proteolytic mechanism in this parasite.