Skip Navigation



Journal of Biochemistry Advance Access published online on September 28, 2007
Journal of Biochemistry, doi:10.1093/jb/mvm181
This Article
Right arrow Advance Access manuscript (PDF)
Right arrow All Versions of this Article:
142/5/553    most recent
mvm181v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Request Permissions
Google Scholar
Right arrow Articles by Nakanishi, N.
Right arrow Articles by Tsubaki, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Nakanishi, N.
Right arrow Articles by Tsubaki, M.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© 2007 The Japanese Biochemical Society

JB Review

Histidine cycle mechanism for the concerted proton/electron transfer from ascorbate to the cytosolic heme b center of cytochrome b561: A unique machinery for the biological transmembrane electron transfer

Nobuyuki Nakanishi{ddagger}, Fusako Takeuchi{dagger} and Motonari Tsubaki{dagger},§,*

From {ddagger}Department of Molecular Science and Material Engineering, Graduate School of Science and Technology, and {dagger}Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan and §CREST, JST, Japan

Corresponding author: Motonari Tsubaki, Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan. TEL +81-(0)78-803-6582, FAX: +81-(0)78-803-6582, E-mail: mtsubaki{at}kobe-u.ac.jp

Received June 26, 2007; Accepted August 18, 2007


  Abstract

Cytochromes b561 are a family of transmembrane proteins found in most eukaryotic cells and contain two heme b prosthetic groups per molecule being coordinated with 4 His residues from 4 different transmembrane {alpha}-helices. Although cytochromes b561 residing in the chromaffin vesicles has long been known to have a role for a neuroendocrine-specific transmembrane electron transfer from extravesicular ascorbate to intravesicular monodehydroascorbate radical to regenerate ascorbate, newly found members were apparently lacking in the sequence for putative ascorbate-binding site but exhibiting a transmembrane ferrireductase activity. We propose that cytochrome b561 has a specific mechanism to facilitate the concerted proton/electron transfer from ascorbate by exploiting a cycle of deprotonated and protonated states of the N{delta}1 atom of the axial His residue at the extravesicular heme center, as an initial step of the transmembrane electron transfer. This mechanism utilizes the well-known electrochemistry of ascorbate for a biological transmembrane electron transfer and might be operative for other type of electron transfer reactions from organic reductants.

Key Words: Ascorbate, Cytochrome b561, Electron transfer, Heme axial His residue, Membrane protein


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.