Mitochondrial outer and inner membrane fusion requires a modifi ed carrier protein

Suzanne Hoppins, Jennifer Horner, Cheng Song, J. Michael McCaffery, Jodi Nunnari

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


In yeast, three proteins are essential for mitochondrial fusion. Fzo1 and Mgm1 are conserved guanosine triphosphatases that reside in the outer and inner membranes, respectively. At each membrane, these conserved proteins are required for the distinct steps of membrane tethering and lipid mixing. The third essential component is Ugo1, an outer membrane protein in the mitochondrial transport protein family. We show that Ugo1 is a modifi ed member of this family, containing three transmembrane domains and existing as a dimer, a structure that is critical for the fusion function of Ugo1. Our functional analysis of Ugo1 indicates that it is required distinctly for both outer and inner membrane fusion after membrane tethering, indicating that it operates at the lipid-mixing step of fusion. This role is distinct from the fusion dynamin-related proteins and thus demonstrates that at each membrane, a single fusion protein is not suffi cient to drive the lipid-mixing step, but instead, this step requires a more complex assembly of proteins.

Original languageEnglish (US)
Pages (from-to)569-581
Number of pages13
JournalJournal of Cell Biology
Issue number4
StatePublished - Feb 23 2009

ASJC Scopus subject areas

  • Cell Biology
  • Medicine(all)


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