Characterization of the Mos10 (Vps60) ESCRT-III complex

The endosomal sorting complex required for transport (ESCRT)-III protein Mos10 (also known as Vps60) forms an alternative ESCRT-III complex in yeast. Here we explored the relationship between the Mos10 complex and the classical Snf7-based complex. Both proteins could in principle form completely independent complexes or mixed complexes. To address this issue, we examined the composition of ESCRT-III in different mutants of the endosomal protein sorting pathway by co-immunoprecipitation. We found that the formation of the Mos10 complex was dependent on the activity of the AAA+ ATPase Vps4. At the same time, loss of Vps4 activity led to an accumulation of the canonical ESCRT-III proteins Snf7, Vps2 and Vps24. In none of the mutants tested a complex could be detected, which only contains Mos10 and no Snf7. We therefore favor the view that Snf7 and Mos10 form mixed complexes, which could play a role in the disassembly of ESCRT-III. To further dissect the interactions among the ESCRT-III subunits, Mos10 mutants were isolated. The L49P mutation in helix ᵯC;1 altered Mos10 localization, while the L150P mutation in helix ᵯC;4 abolished membrane association. A potential explanation for the effect of the L49P mutation on Mos10 function is suggested by AlphaFold modeling.