Transmembrane Helices Mediate the Formation of a Stable Ternary Complex of B5R, cyt b5, and SCD1

Authors

Jiemin Shen
Gang Wu
Ah-Lim Tsai
Ming Zhou

Publication Date

9-12-2022

Journal

Communications Biology

DOI

10.1038/s42003-022-03882-z

PMID

36097052

PMCID

PMC9468158

PubMedCentral® Posted Date

9-12-2022

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes

Keywords

Animals, Cytochromes b, Electron Transport, Electrons, Mammals, Oxidoreductases, Enzymes, Enzymes

Abstract

Mammalian cytochrome b5 (cyt b5) and cytochrome b5 reductase (b5R) are electron carrier proteins for membrane-embedded oxidoreductases. Both b5R and cyt b5 have a cytosolic domain and a single transmembrane (TM) helix. The cytosolic domains of b5R and cyt b5 contain cofactors required for electron transfer, but it is not clear if the TM helix has function beyond being an anchor to the membrane. Here we show that b5R and cyt b5 form a stable binary complex, and so do cyt b5 and stearoyl-CoA desaturase-1 (SCD1). We also show that b5R, cyt b5 and SCD1 form a stable ternary complex. We demonstrate that the TM helices are required for the assembly of stable binary and ternary complexes where electron transfer rates are greatly enhanced. These results reveal a role of the TM helix in cyt b5 and b5R, and suggest that an electron transport chain composed of a stable ternary complex may be a general feature in membrane-embedded oxidoreductases that require cyt b5 and b5R.

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