Florian Lübben
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Signaling mechanisms regulating protein transport
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Abstract
Mitochondria require more than 1000 different proteins to fulfill their functions. The vast majority of these proteins are synthesized by cytosolic ribosomes and have to be imported into the organelle, sorted to their correct location and assembled into their native protein complex. Since most precursor proteins enter the mitochondria through the TOM complex, alpha-helical proteins are integrated into the outer membrane through the funghi-specific MIM complex which is composed of the two subunits Mim1 and Mim2. The cytosolic kinase Ck2 phosphorylates the two N-terminal serine residues S12 and S16 of Mim1 thereby enhancing the stability and also effecting the import and assembly of certain substrates. The three TOM receptors Tom20, Tom22 and Tom70 as well as the small TOM proteins Tom5, Tom6 and Tom7 belong to the family of alpha-helical proteins following a Mim1-dependent import pathway. Furthermore, it could be shown, that the MIM complex has a currently unknown role in the assembly of beta-barrel proteins like Tom40. Thus, the MIM complex is involved in the biogenesis of the entire TOM complex.
Methods
- Yeast cell culture
- Isolation of mitochondria
- Cell free translation of membrane proteins
- In vitro protein import assays
- SDS-PAGE, Phos-Tag SDS-PAGE, Blue Native PAGE
