(A, D) Fusion is rescued by a double positive charge swap in (A) but not by the presence of neutral amino acids in (D). Mitochondrial morphology and quantification of ∆fzo1 cells expressing the indicated Fzo1 variants, co-expressing a mitochondrial-targeted GFP plasmid, analyzed as in Fig 1D. Scale bar: 5 μm. (B, C) Triple salt bridge swap between residues in positions 182, 335, and 464 rescues Fzo1 ubiquitylation in (B) and fusion capacity in (C). The indicated Fzo1 mutant variants were analyzed for ubiquitylation as in Fig 1B and for fusion capacity as in Fig 1D. PoS, PonceauS staining.