Electron Exchange between Fe(II)-Horse Spleen Ferritin and Co(III)/Mn(III) Reconstituted Horse Spleen andAzotobacter vinelandiiFerritins

• DOI: 10.1021/bi060164d
• Publication Date: 2006-05-02T04:31:43Z
• Authors: Bo Zhang; John N. Harb; Robert C. Davis; Sang Choi; Jae-Woo Kim; Tim Miller; Sang-Hyon Chu; Gerald D. Watt
• Keywords: Azotobacter vinelandii; Azotobacter

Azotobacter vinelandii bacterioferritin (AvBF) containing 800−1500 Co or Mn atoms as Co(III) and Mn(III) oxyhydroxide cores (Co-AvBF, Mn-AvBF) was synthesized by the same procedure used previously for horse spleen ferritin (HoSF). The kinetics of reduction Co-AvBF Mn-AvBF ascorbic acid are first-order in each reactant. rate constant (8.52 M-1 min-1) is ∼12 times larger than that (0.72 min-1), which consistent with a previous observation Mn-HoSF reduced ∼10-fold faster Co-HoSF [Zhang, B. et al. (2005) Inorg. Chem. 44, 3738−3745]. rates M-AvBF (M = Mn) more twice corresponding M-HoSF. HoSF Fe(II) (Fe(II)-HoSF), prepared methyl viologen CO, also reduces M-HoSF species, both remaining within ferritin, suggesting electrons transfer through shell. Electron from Fe(II)-HoSF to occurs at ∼3 Co-HoSF, indicating AvBF accessible HoSF. presence nonconductive (SiO2) conductive (gold) surfaces known bind ferritins enhances electron transfer. A ∼4-fold increase apparent reaction observed gold. Although (SiO2 gold) enhance providing binding sites molecular interaction, results show different mineral bound gold surface substrate so direct contact reacting molecules not required.