The product of uncI gene in F ₁ F _o -ATP synthase operon plays a chaperone-like role to assist c -ring assembly

Abstract

Bacterial operons for F1Fo-ATP synthase typically include an uncI gene that encodes a function-unknown small hydrophobic protein.When we expressed a hybrid F 1Fo (F1 from thermophilic Bacillus PS3 and Na ؉ -translocating Fo from Propionigenium modestum) in Escherchia coli cells, we found that uncI derived from P. modestum was indispensable to produce active enzyme; without uncI, csubunits in F 1Fo existed as monomers but not as functional c11-ring. When uncI was expressed from another plasmid at the same time, active F 1Fo with c11-ring was produced. A plasmid containing only uncI and c-subunit gene produced c 11-ring, but a plasmid containing only c-subunit gene did not. Direct interaction of UncI protein with c-subunits was suggested from copurification of His-tagged UncI protein and c-subunits, both in the state of c 11-ring and c-monomers. Na ؉ induced dissociation of His-tagged UncI protein from c 11-ring but not from c-monomers. These results show that UncI is a chaperone-like protein that assists c 11-ring assembly from c-monomers in the membrane.protein folding ͉ membrane protein ͉ Na ϩ transport

Engineering rotor ring stoichiometries in the ATP synthase

“…Spectroscopic data indeed show that the central stalk (subunits γ and ε) of the I. tartaricus ATP synthase is able to interact with c n rings of variable diameter [at least from n = 11-15 (5.5 and 6.5 nm in diameter, respectively)] with wild type-like affinity. Our findings are consistent with the observation that a given F 1 domain derived from either E. coli or Bacillus PS3 can dock either with its native c 10 ring or with c 11 rings from Propionigenium modestum, forming chimeric F 1 F o ATP synthases (39,40). Taken together, these studies suggest a high degree of structural compliance in the assembly of the rotor subcomplex (c n γε).…”

Assembly of the Rotor Component of Yeast Mitochondrial ATP Synthase Is Enhanced When Atp9p Is Supplied by Atp9p-Cox6p Complexes

“…Purified subunit c (Atp9p) of E. coli (46) and thermophilic Bacillus PS3 (47) have been reported to spontaneously oligomerize into rings from detergent solutions. Other studies, however, indicate that conversion of bacterial subunit c to the ring is mediated by the uncI gene product of E. coli (48,49). Ring formation in S. cerevisiae has also been shown to require a protein encoded by the N-terminal half of the yeast nuclear ATP25 gene (50).…”

Regulation of the F1F0-ATP Synthase Rotary Nanomotor in its Monomeric-Bacterial and Dimeric-Mitochondrial Forms

“…However, instead of additional regulatory proteins, unique polar interactions at the rotorstator interface of the F 1 subunits allow almost exclusively unidirectional rotation in the ATP synthase direction for this enzyme [31]. To our knowledge, only two other bacterial proteins have been found encoded in the atp operon in addition to the eight core subunits of bacterial F 1 F 0 (α, β, γ, δ, ε, a, b, c); these two proteins are encoded by the unc-I and urf-6 genes that correspond, respectively, to an assembly factor of the c-ring [32] and to majastridin, a cytosolic protein nonassociated with the Rhodospirillum blasticus ATP synthase [33]. In contrast, the gene encoding the 11-kDa protein of P. denitrificans is located upstream to both atp operons (one for F 0 and another for F 1 subunits) already sequenced on chromosome II of P. denitrificans (see Morales-Ríos et al 2008, submitted, and the following link: http://genome.jgi-psf.org/finished_microbes/parde/parde.home.htm).…”