HOQNO interaction with cytochrome b in succinate:menaquinone oxidoreductase from Bacillus subtilis

FEBS Letters

Hägerhäll, Cecilia²  Konstantinov, Alexandre A.¹  Hederstedt, Lars²  Smirnova, Irina A.¹ 

[1] A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119 899, Russian Federation;Department of Microbiology, Lund University, Sölvegatan 21, S-22362 Lund, Sweden

关键词: 2-n-Heptyl 4-hydroxyquinoline-N-oxide;    Succinate quinone reductase;    Cytochrome b;    Bacillus subtilis;    Menasemiquinone;    Complex II;    DCPIP;    2;    6-dichlorophenolindophenol;    HOQNO;    2-n-heptyl4-hydroxyquinoline-N-oxide;    MQ;    menaquinone;    MOPS;    3-(N-morpholino)propanesulfonicFXX acid;    PMS;    phenazine methosulfate;    UQ;    ubiquinone;    SQR;    succinate quinone oxidoreductase;    TTFA;    α-thenoyltrifluoroacetone;   

DOI  :  10.1016/0014-5793(94)01442-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

2-n-Heptyl4-hydroxyquinoline-N-oxide (HOQNO) inhibits the succinate:quinone oxidoreductase activity of isolated and membrane-bound succinate:menaquinone oxidoreductase of B. subtilis. The inhibition pattern resembles closely that observed for α-thenoyltrifluoroacetone and carboxins in the mitochondrial succinate:ubiquinone oxidoreductase: ca. 90% of the activity is highly sensitive to HOQNO (K _i ca. 0.2 μM for the isolated enzyme) whereas the rest 10% proves to be resistant to the inhibitor. HOQNO binding is shown to perturb the absorption spectrum of the ferrous di-heme cytochrome b of the B. subtilis succinate:quinone oxidoreductase both in the α and Soret bands. In addition, the inhibitor is shown to bring about a negative shift of E _m of the low-potential heme b. It is suggested that HOQNO interacts with a menasemiquinone binding site near the low-potential heme and suppresses the MQ^.−-to-MQH₂ step of the quinone reductase reaction but allows partly for the MQ-to-MQ^.− transition to occur; dismutation of MQ^. formed in the latter reaction to MQ and MQH₂ may account for the 10% of the enzyme activity insensitive to HOQNO.

【 授权许可】

Unknown