Methoxyacrylate stilbene

The mutation Glyl43Ala is unlikely to cause a structural perturbation in the absence of inhibitors, consequently, the activity of the bc complex is not greatly reduced. We have created a series of mutations in position 143 to test the effect of the size of the amino acid in position 143 (Table 1). The table shows that the mutation of glycine to alanine gives high resistance to methoxyacrylate-stilbene with high activity (approximately 60% of the wild type level) while in the other mutants (Ser, Cys, Pro) the activity is 10% of the wild type level or less with valine, almost no activity was observed. Despite, the differences in the residual activity, the I50 for MOA-stilhene is the same in all mutants but proline. 

Other recent reports further confirmed the different locations occupied by the extrinsic [2Fe 2S] domain in different crystals. An intermediate location was reported by Iwata et alf in a new crystal form which places this domain 27.5 A from Cyt ci and 13 A from the Qo site. Kim, (D) Xia, (C-A) Yu, (J-Z) Xia, Kachurin, Zhang, (L) Yu and Deisenhofer further examined crystal stmctures of bovine mitochondrial Cyt-bc complexes with inhibitors bound to the Qo and/or Qj (j.e., Q ) sites. Binding of the Qq-site inhibitor UHDBT (5-undecyl-6-hydroxy-4,7-dioxobenzothiazol) and stigmatellin was found to result in the [2Fe 2S] domain being at the Cyt b interface, whereas binding of myxothiazol or MOAS (methoxyacrylate-stilbene) led to the release of this domain. The native complex with a vacant Qo site was found to have a structure intermediate between these two extremes. 

Figure 4 Famoxate and methoxyacrylate stilbene, respectively two inhibitors...

Figure 5 Famoxate and methoxyacrylate stilbene occupy slightly different regions of the Qo binding site.

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