Synthesis and Characterization of New Piperazine-Type Inhibitors for Mitochondrial NADH-Ubiquinone Oxidoreductase (Complex I)

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• 作者：Naoya Ichimaru ; Masatoshi Murai ; Nobuyuki Kakutani ; Junko Kako ; Atsushi Ishihara ; Yoshiaki Nakagawa ; Takaaki Nishioka ; Takao Yagi ; Hideto Miyoshi
• 刊名：Biochemistry
• 出版年：2008
• 出版时间：October 7, 2008
• 年：2008
• 卷：47
• 期：40
• 页码：10816-10826
• 全文大小：317K
• 年卷期：v.47,no.40(October 7, 2008)
• ISSN：1520-4995

文摘

The mode of action of Δlac-acetogenins, strong inhibitors of bovine heart mitochondrial complex I, is different from that of traditional inhibitors such as rotenone and piericidin A [Murai, M., et al. (2007) Biochemistry 46, 6409−6416]. As further exploration of these unique inhibitors might provide new insights into the terminal electron transfer step of complex I, we drastically modified the structure of Δlac-acetogenins and characterized their inhibitory action. In particular, on the basis of structural similarity between the bis-THF and the piperazine rings, we here synthesized a series of piperazine derivatives. Some of the derivatives exhibited very potent inhibition at nanomolar levels. The hydrophobicity of the side chains and their balance were important structural factors for the inhibition, as is the case for the original Δlac-acetogenins. However, unlike in the case of the original Δlac-acetogenins, (i) the presence of two hydroxy groups is not crucial for the activity, (ii) the level of superoxide production induced by the piperazines is relatively high, (iii) the inhibitory potency for the reverse electron transfer is remarkably weaker than that for the forward event, and (iv) the piperazines efficiently suppressed the specific binding of a photoaffinity probe of natural-type acetogenins ([¹²⁵I]TDA) to the ND1 subunit. We therefore conclude that the action mechanism of the piperazine series differs from that of the original Δlac-acetogenins. The photoaffinity labeling study using a newly synthesized photoreactive piperazine ([¹²⁵I]AFP) revealed that this compound binds to the 49 kDa subunit and an unidentified subunit, not ND1, with a frequency of ∼1:3. A variety of traditional complex I inhibitors as well as Δlac-acetogenins suppressed the specific binding of [¹²⁵I]AFP to the subunits. The apparent competitive behavior of inhibitors that seem to bind to different sites may be due to structural changes at the binding site, rather than occupying the same site. The meaning of the occurrence of diverse inhibitors exhibiting different mechanisms of action is discussed in light of the functionality of the membrane arm of complex I.