The assembly factor Atp11p binds to the β-subunit of the mitochondrial F1-ATPase

Abstract

Atp11p is a protein of Saccharomyces cerevisiae required for the assembly of the F1 component of the mitochondrial F1F0-ATP synthase. This study presents evidence that Atp11p binds selectively to the β-subunit of F1. Under conditions in which avidin-Sepharose beads specifically adsorbed biotinylated Atp11p from yeast mitochondrial extracts, the F1 β-subunit coprecipitated with the tagged Atp11p protein. Binding interactions between Atp11p and the entire β-subunit of F1 or fragments of the β-subunit were also revealed by a yeast two-hybrid screen: Atp11p bound to a region of the nucleotide-binding domain of the β-subunit located between Gly114 and Leu318. Certain elements of this sequence that would be accessible to Atp11p in the free β-subunit make contact with adjacent α-subunits in the assembled enzyme. This observation suggests that the α-subunits may exchange for bound Atp11p during the process of F1 assembly.