PMID: 26071601

Authors:

Yu F, He F, Yao H, Wang C, Wang J, Li J, Qi X, Xue H, Ding J, Zhang P

Title:

Structural basis of intramitochondrial phosphatidic acid transport mediated by Ups1-Mdm35 complex.

Journal:

EMBO Rep. 2015 Jun 12. pii: e201540137.

Abstract:

Ups1 forms a complex with Mdm35 and is critical for the transport of phosphatidic acid (PA) from the mitochondrial outer membrane to the inner membrane. We report the crystal structure of the Ups1-Mdm35-PA complex and the functional characterization of Ups1-Mdm35 in PA binding and transfer. Ups1 features a barrel-like structure consisting of an antiparallel beta-sheet and three alpha-helices. Mdm35 adopts a three-helical clamp-like structure to wrap around Ups1 to form a stable complex. The beta-sheet and alpha-helices of Ups1 form a long tunnel-like pocket to accommodate the substrate PA, and a short helix alpha2 acts as a lid to cover the pocket. The hydrophobic residues lining the pocket and helix alpha2 are critical for PA binding and transfer. In addition, a hydrophilic patch on the surface of Ups1 near the PA phosphate-binding site also plays an important role in the function of Ups1-Mdm35. Our study reveals the molecular basis of the function of Ups1-Mdm35 and sheds new light on the mechanism of intramitochondrial phospholipid transport by the MSF1/PRELI family proteins.