PT  - JOURNAL ARTICLE
AU  - Yi-Yun Cheng
AU  - Yun-Fang Huang
AU  - Hsin-Hui Lin
AU  - Wun-Shaing Wayne Chang
AU  - Ping-Chiang Lyu
TI  - The ligand-mediated affinity of escort proteins determines the directionality of lipophilic cargo transport
AID  - 10.1101/415984
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 415984
4099  - http://biorxiv.org/content/early/2018/12/07/415984.short
4100  - http://biorxiv.org/content/early/2018/12/07/415984.full
AB  - Intracellular cargo transport is a highly dynamic process. In eukaryotic cells, the uptake and release of lipophilic ligands are executed by escort proteins. However, how these carriers control the directionality of cargo trafficking remains unclear. Here, we have elucidated the unliganded structure of an archetypal fatty acid-binding protein (FABP) and found that it possesses stronger binding affinity than its liganded counterpart towards empty nanodiscs. Titrating unliganded FABP and nanodiscs with long-chain fatty acids (LCFAs) rescued the broadening of FABP cross-peak intensities in HSQC spectra due to decreased protein-membrane interaction. Crystallographic studies revealed that the tails of bound LCFAs obstructed the charged interfaces of the FABP–nanodisc complexes. We conclude that the lipophilic ligands, by taking advantage of escort proteins with high conformational homogeneity and nanodiscs as the third interaction partner involved in this transport study, participate directly in the control of their own transportation in an irreversible, unidirectional fashion.