Limits...
Chaperones of F1-ATPase.

Ludlam A, Brunzelle J, Pribyl T, Xu X, Gatti DL, Ackerman SH - J. Biol. Chem. (2009)

Bottom Line: One important feature of this model was the prediction that as long as Atp11p is bound to beta and Atp12p is bound to alpha, the two F(1) subunits cannot interact at either the catalytic site or the noncatalytic site interface.Here we present the structures of Atp11p from Candida glabrata and Atp12p from Paracoccus denitrificans, and we show that some features of the Wang model are correct, namely that binding of the chaperones to alpha and beta prevents further interactions between these F(1) subunits.However, Atp11p and Atp12p do not resemble alpha or beta, and it is instead the F(1) gamma subunit that initiates the release of the chaperones from alpha and beta and their further assembly into the mature complex.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.

ABSTRACT
Mitochondrial F(1)-ATPase contains a hexamer of alternating alpha and beta subunits. The assembly of this structure requires two specialized chaperones, Atp11p and Atp12p, that bind transiently to beta and alpha. In the absence of Atp11p and Atp12p, the hexamer is not formed, and alpha and beta precipitate as large insoluble aggregates. An early model for the mechanism of chaperone-mediated F(1) assembly (Wang, Z. G., Sheluho, D., Gatti, D. L., and Ackerman, S. H. (2000) EMBO J. 19, 1486-1493) hypothesized that the chaperones themselves look very much like the alpha and beta subunits, and proposed an exchange of Atp11p for alpha and of Atp12p for beta; the driving force for the exchange was expected to be a higher affinity of alpha and beta for each other than for the respective chaperone partners. One important feature of this model was the prediction that as long as Atp11p is bound to beta and Atp12p is bound to alpha, the two F(1) subunits cannot interact at either the catalytic site or the noncatalytic site interface. Here we present the structures of Atp11p from Candida glabrata and Atp12p from Paracoccus denitrificans, and we show that some features of the Wang model are correct, namely that binding of the chaperones to alpha and beta prevents further interactions between these F(1) subunits. However, Atp11p and Atp12p do not resemble alpha or beta, and it is instead the F(1) gamma subunit that initiates the release of the chaperones from alpha and beta and their further assembly into the mature complex.

Show MeSH

Related in: MedlinePlus

A possible interaction of Atp12p with F1 α. A, superposition of the yeast F1 γ subunit (cyan) to P. denitrificans Atp12p (yellow). The C-terminal helices of Atp12p are colored in red. B, predicted interaction of P. denitrificans Atp12p with yeast F1 α (green), based on the relative position of the α and γ subunits in yeast F1. (PDB code 2hld (Mol 1)).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2719352&req=5

Figure 7: A possible interaction of Atp12p with F1 α. A, superposition of the yeast F1 γ subunit (cyan) to P. denitrificans Atp12p (yellow). The C-terminal helices of Atp12p are colored in red. B, predicted interaction of P. denitrificans Atp12p with yeast F1 α (green), based on the relative position of the α and γ subunits in yeast F1. (PDB code 2hld (Mol 1)).

Mentions: Atp11p and Atp12p are present in the mitochondrial matrix in small amounts, comparable with those of unassembled α and β subunits. In the absence of one of these subunits, as F1 cannot be assembled, the concentration of the other subunit exceeds that of the cognate chaperone and the subunit aggregates. In S. cerevisiae strains harboring a disruption of the nuclear gene encoding either the α or the β subunit, insoluble aggregates are formed even in the presence of normal amounts of functioning Atp11p and Atp12p (4). During F1 assembly, the formation of Atp11p:β and Atp12p:α intermediates may not promote directly the formation of the physiological α:β dimers, but rather act as decoys preventing the formation of nonphysiological α:α, β:β, and α:β complexes. Although this action would be critical to prevent aggregation, it also requires an initial trigger to form at least one physiological α:β dimer devoid of chaperones. After this initial event, it is conceivable that successive bindings of an Atp11p-β or Atp12p-α complex to an α:β dimer might produce a conformational change that decreases the affinity of the chaperones for their target proteins. Analysis of the F1 assembly intermediates in yeast cells, in which the nuclear gene encoding the F1 γ subunit was disrupted (), suggests that the γ subunit is the trigger factor necessary for the initial chaperone release. In the absence of structures of the Atp11p:β and Atp12p:α intermediates, it is not possible to know exactly how the γ subunit interacts with these complexes. However, a side-by-side visual inspection of Atp12p and γ reveals that the most peripheral section of the long coiled-coil of the γ subunit is remarkably similar to the C-terminal helical fragment of Atp12p (Fig. 7A), which was shown to be essential for activity. If the C-terminal helices of Atp12p are superimposed to the coiled-coil tail of the yeast γ subunit bound to α, then the surface of Atp12p complements very well the surface of the yeast α subunit (Fig. 7B), providing a reasonable guess of how the two proteins interact. The finding of a possible molecular mimicry between the C-terminal region of Atp12p and the coiled-coil tail of γ raises the possibility that F1 assembly may start with the γ subunit displacing Atp12p from the Atp12p:α heterodimer.


Chaperones of F1-ATPase.

Ludlam A, Brunzelle J, Pribyl T, Xu X, Gatti DL, Ackerman SH - J. Biol. Chem. (2009)

A possible interaction of Atp12p with F1 α. A, superposition of the yeast F1 γ subunit (cyan) to P. denitrificans Atp12p (yellow). The C-terminal helices of Atp12p are colored in red. B, predicted interaction of P. denitrificans Atp12p with yeast F1 α (green), based on the relative position of the α and γ subunits in yeast F1. (PDB code 2hld (Mol 1)).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2719352&req=5

Figure 7: A possible interaction of Atp12p with F1 α. A, superposition of the yeast F1 γ subunit (cyan) to P. denitrificans Atp12p (yellow). The C-terminal helices of Atp12p are colored in red. B, predicted interaction of P. denitrificans Atp12p with yeast F1 α (green), based on the relative position of the α and γ subunits in yeast F1. (PDB code 2hld (Mol 1)).
Mentions: Atp11p and Atp12p are present in the mitochondrial matrix in small amounts, comparable with those of unassembled α and β subunits. In the absence of one of these subunits, as F1 cannot be assembled, the concentration of the other subunit exceeds that of the cognate chaperone and the subunit aggregates. In S. cerevisiae strains harboring a disruption of the nuclear gene encoding either the α or the β subunit, insoluble aggregates are formed even in the presence of normal amounts of functioning Atp11p and Atp12p (4). During F1 assembly, the formation of Atp11p:β and Atp12p:α intermediates may not promote directly the formation of the physiological α:β dimers, but rather act as decoys preventing the formation of nonphysiological α:α, β:β, and α:β complexes. Although this action would be critical to prevent aggregation, it also requires an initial trigger to form at least one physiological α:β dimer devoid of chaperones. After this initial event, it is conceivable that successive bindings of an Atp11p-β or Atp12p-α complex to an α:β dimer might produce a conformational change that decreases the affinity of the chaperones for their target proteins. Analysis of the F1 assembly intermediates in yeast cells, in which the nuclear gene encoding the F1 γ subunit was disrupted (), suggests that the γ subunit is the trigger factor necessary for the initial chaperone release. In the absence of structures of the Atp11p:β and Atp12p:α intermediates, it is not possible to know exactly how the γ subunit interacts with these complexes. However, a side-by-side visual inspection of Atp12p and γ reveals that the most peripheral section of the long coiled-coil of the γ subunit is remarkably similar to the C-terminal helical fragment of Atp12p (Fig. 7A), which was shown to be essential for activity. If the C-terminal helices of Atp12p are superimposed to the coiled-coil tail of the yeast γ subunit bound to α, then the surface of Atp12p complements very well the surface of the yeast α subunit (Fig. 7B), providing a reasonable guess of how the two proteins interact. The finding of a possible molecular mimicry between the C-terminal region of Atp12p and the coiled-coil tail of γ raises the possibility that F1 assembly may start with the γ subunit displacing Atp12p from the Atp12p:α heterodimer.

Bottom Line: One important feature of this model was the prediction that as long as Atp11p is bound to beta and Atp12p is bound to alpha, the two F(1) subunits cannot interact at either the catalytic site or the noncatalytic site interface.Here we present the structures of Atp11p from Candida glabrata and Atp12p from Paracoccus denitrificans, and we show that some features of the Wang model are correct, namely that binding of the chaperones to alpha and beta prevents further interactions between these F(1) subunits.However, Atp11p and Atp12p do not resemble alpha or beta, and it is instead the F(1) gamma subunit that initiates the release of the chaperones from alpha and beta and their further assembly into the mature complex.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.

ABSTRACT
Mitochondrial F(1)-ATPase contains a hexamer of alternating alpha and beta subunits. The assembly of this structure requires two specialized chaperones, Atp11p and Atp12p, that bind transiently to beta and alpha. In the absence of Atp11p and Atp12p, the hexamer is not formed, and alpha and beta precipitate as large insoluble aggregates. An early model for the mechanism of chaperone-mediated F(1) assembly (Wang, Z. G., Sheluho, D., Gatti, D. L., and Ackerman, S. H. (2000) EMBO J. 19, 1486-1493) hypothesized that the chaperones themselves look very much like the alpha and beta subunits, and proposed an exchange of Atp11p for alpha and of Atp12p for beta; the driving force for the exchange was expected to be a higher affinity of alpha and beta for each other than for the respective chaperone partners. One important feature of this model was the prediction that as long as Atp11p is bound to beta and Atp12p is bound to alpha, the two F(1) subunits cannot interact at either the catalytic site or the noncatalytic site interface. Here we present the structures of Atp11p from Candida glabrata and Atp12p from Paracoccus denitrificans, and we show that some features of the Wang model are correct, namely that binding of the chaperones to alpha and beta prevents further interactions between these F(1) subunits. However, Atp11p and Atp12p do not resemble alpha or beta, and it is instead the F(1) gamma subunit that initiates the release of the chaperones from alpha and beta and their further assembly into the mature complex.

Show MeSH
Related in: MedlinePlus