Mutational analysis of the N-terminus of Bax in yeast and mammalian models [121, 126, 133, 134]

SequenceProteinBinding to mitochondriaCytochrome c release
YeastMammalsYeastMammals
(1) Role of ART and Proline residues at positions 8 and 13
-P8RGGGP13-full length Bax+/−+/−+/−+/−
BaxΨ/ΔART++++++++++++
-G8RGGGG13-ART mutant+++n.d.+++n.d.
-V8RGGGV13-ART mutantn.d.+++n.d.+++
-V8RGGGP13-ART mutantn.d.+/−n.d.+/−
-P8RGGGV13-ART mutantn.d.+++n.d.+++
(2) Role of helix α1

-A24LLL27-
BaxΨ/ΔART
+++
+++
+++
+++
BaxΨ/ΔART
ΔHα1
n.d.

n.d.


-R24LLL27-
BaxΨ/ΔART
Hα1 mutant
++

-A24LGV27-
BaxΨ/ΔART
Hα1 mutant
++++++
(3) Interaction between ART and BH2 (helix α7/8)
-P8RGGGP13-
-I152QDQG156-
full length human Bax+/−+/−+/−+/−
-P8EGGGP13-
-I152QDQG156-
ART mutant+++n.d.+++n.d.
-P8RGGGP13-
-I152QKQG156-
BH2 mutant+++n.d.+++n.d.
-P8EGGGP13-
-I152QKQG156-
ART mutant
BH2 mutant
n.d.n.d.

(1) The substitution of prolines 8 and 13, like the complete deletion of the 20 N-terminal residues, increase Bax binding and activity both in yeast and mammals; (2) substitutions in helix α1 decrease the binding of BaxΨ in mammals. The decrease is partly visible in yeast; (3) individual point mutations inverting charges in ART and in BH2 induce stimulation of Bax in yeast, but a double charge change revert to the wild-type behavior of Bax, suggesting the existence of an interaction between charged residues in these two domains, stabilizing the inactive conformation. Bold residues indicate mutations. −: inactive; n.d.: not determined; +/−: poorly active; +: active; +++: strongly active