Crystal structures of a nicotine MATE transporter provide insight into its mechanism of substrate transport.

A transporter of the multidrug and toxic compound extrusion (MATE) family, Nicotiana tabacum MATE2 (NtMATE2), is located in the vacuole membrane of the tobacco plant root and is involved in the transportation of nicotine, a secondary or specialized metabolic compound in Solanaceae. Here, we report the crystal structures of NtMATE2 in its outward-facing forms. The overall structure has a bilobate V-shape with pseudo-symmetrical assembly of the N- and C-lobes.

Structural Basis for the Function of the β-Barrel Assembly-Enhancing Protease BepA.

The β-barrel assembly machinery (BAM) complex mediates the assembly of β-barrel membrane proteins in the outer membrane. BepA, formerly known as YfgC, interacts with the BAM complex and functions as a protease/chaperone for the enhancement of the assembly and/or degradation of β-barrel membrane proteins. To elucidate the molecular mechanism underlying the dual functions of BepA, its full-length three-dimensional structure is needed.

Crystal Structure of a Plant Multidrug and Toxic Compound Extrusion Family Protein.

The multidrug and toxic compound extrusion (MATE) family of proteins consists of transporters responsible for multidrug resistance in prokaryotes. In plants, a number of MATE proteins were identified by recent genomic and functional studies, which imply that the proteins have substrate-specific transport functions instead of multidrug extrusion. The three-dimensional structure of eukaryotic MATE proteins, including those of plants, has not been reported, preventing a better understanding of the molecular mechanism of these proteins.

Tunnel Formation Inferred from the I-Form Structures of the Proton-Driven Protein Secretion Motor SecDF.

Protein secretion mediated by SecYEG translocon and SecA ATPase is enhanced by membrane-embedded SecDF by using proton motive force. A previous structural study of SecDF indicated that it comprises 12 transmembrane helices that can conduct protons and three periplasmic domains, which form at least two characterized transition states, termed the F and I forms. We report the structures of full-length SecDF in I form at 2.