Saccharomyces cerevisiae Porin Pore Forms Complexes with Mitochondrial Outer Membrane Proteins Om14p and Om45p

Abstract

Background: Currently, no information is available about the association of the mitochondrial porin pore with the major outer membrane proteins Om14p and Om45p. Results: Por1p forms complexes with Om14p and Om45p. Conclusion: Molecular organization of the porin pore and its interaction with the inner membrane is influenced by Om14p and Om45p. Significance: The newly identified protein complex improves the understanding of mitochondrial transport processes.

A novel import route for an N-anchor mitochondrial outer membrane protein aided by the TIM23 complex

“…Both the N-terminal segments of Om45 and Tom70 can guide the C-terminal domain of Om45 to the IMS via this pathway. Finally, Om45 is re-inserted into the OM from the IMS side and assembled into a complex with, for example, Om14 [11]. Although a Mim1 dependence of the final step of Om45 assembly is reported in a parallel study [19], involvement of other component(s), if any, in this new pathway remains to be investigated in future studies.…”

“…The protein level of Om45 increases under nonfermentable conditions [10], and the role of Om45 in the regulation of porin channels was proposed [11]. Om45 has a stretch of hydrophobic residues near the N-terminus (residues 5-22) like Tom20 and Tom70, both of which are anchored to the OM by their N-terminal TM segments and expose the C-terminal domains to the cytosol (N in -C out topology).…”

The presequence pathway is involved in protein sorting to the mitochondrial outer membrane

“…Anti-His antibodies bound to the Om45 His complex in mitoplasts, but not in intact mitochondria (Fig 1E). Om45 His was properly assembled, shown by the co-purification of the two partner proteins porin and Om14 ( Supplementary Fig S1B) [18]. Additionally, the His-tag or a green fluorescent protein (GFP) fused to the C-terminus of Om45 was only accessible to protease after opening of the outer membrane ( Supplementary Fig S1C and D).…”

Interaction network of the mitochondrial outer membrane protein Mcp3

“…Yet, its function is still ill defined. Recently, it was reported to interact with porin (Por1) and Om14, another S. cerevisiae exclusive MOM protein of unknown function . In the same work, a role for Om45 in coordination of metabolite flux in and out of the organelle via porin channels in the MOM and transporter proteins of the carrier type in the MIM was proposed.…”

“…This might be a first hint to a functional relationship of the Mcp3 interactor Aim19 with Om45. A quite tempting but still very speculative hypothesis would be that Mcp3/Om45/Aim19 are involved in a contact between the MOM and MIM that could be involved in mitochondrial metabolite flux as was suggested for Om45 .…”