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Abstract

The closely related proteins prohibitin (p32) and prohibitone (p37) are evolutionarily conserved with homologues found from cyanobacteria to man. They are thought to be exclusively mitochondrial and have been assigned many-rather different-functions, ranging from a role in lifespan, in mitochondrial inheritance and as chaperones of mitochondrial proteases in yeast. Evidence for a localisation outside of mitochondria has been brought forward in mammalian cells, where they influence cell-cycle progression and are found in association with cell surface receptors. We have employed a yeast two-hybrid screen to identify other interacting proteins and have identified α-actinin and annexin A2 as binding partners for prohibitin and prohibitone. Coprecipitation experiments supported the putative binding between prohibitin and prohibitone on the one hand and annexin A2 or α-actinin on the other hand in intact cells. Surface plasmon resonance analysis was used to determine relative affinities between prohibitin and α-actinin and between prohibitone and annexin A2 and α-actinin, respectively. We further show that prohibitin and prohibitone can also form homomeric (preferentially tetrameric) and heteromultimeric complexes, with significant affinities.