Protonation/deprotonation-driven switch for the redox stability of low-potential ferredoxin

Wada, K.; Kobayashi, K.; Era, I.; Isobe, Y.; Kamimura, T.; Marukawa, M.; Nagae, T.; Honjo, K.; Kaseda, N.; Motoyama, Y.; Inoue, K.; Sugishima, M.; Kusaka, K.; Yano, N.; Fukuyama, K.; Mishima, M.; Kitagawa, Y.; Unno, M.

doi:10.1101/2024.09.12.612615

bioRxiv · 10.1101/2024.09.12.612615

Protonation/deprotonation-driven switch for the redox stability of low-potential ferredoxin

Wada, K.·Kobayashi, K.·Era, I.·Isobe, Y.·Kamimura, T.·Marukawa, M.·Nagae, T.·Honjo, K.·Kaseda, N.·Motoyama, Y.·Inoue, K.·Sugishima, M.·Kusaka, K.·Yano, N.·Fukuyama, K.·Mishima, M.·Kitagawa, Y.·Unno, M.

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Abstract

Ferredoxin is a small iron-sulfur protein and acts as an electron carrier. Low-potential ferredoxins harbor [4Fe-4S] cluster(s), which play(s) a crucial role as the redox center. Low-potential ferredoxins are able to cover a wide range of redox potentials (-700 to -200 mV); however, the mechanisms underlying the factors which control the redox potential are still enigmatic. Here, we determined the neutron structure of ferredoxin from Bacillus thermoproteolyticus, and experimentally revealed the exact hydrogen-bonding network involving the [4Fe-4S] cluster. The density functional theory calculations based on the hydrogen-bonding network revealed that protonation states of the sidechain of Asp64 close to the [4Fe-4S] cluster critically affected the stability of the reduced state in the cluster. These findings provide the first identification of the intrinsic control factor of redox potential for the [4Fe-4S] cluster in low-potential ferredoxins.

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Wada, K., Kobayashi, K., Era, I., Isobe, Y., Kamimura, T., Marukawa, M., Nagae, T., Honjo, K., Kaseda, N., Motoyama, Y., Inoue, K., Sugishima, M., Kusaka, K., Yano, N., Fukuyama, K., Mishima, M., Kitagawa, Y., Unno, M.. 2024-09-14. Protonation/deprotonation-driven switch for the redox stability of low-potential ferredoxin. https://doi.org/10.1101/2024.09.12.612615

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