Crystal structure of a two-subunit TrkA octameric gating ring assembly.

Area of Science:

• Structural Biology
• Biochemistry
• Molecular Biology

Background:

• The TM1088 locus in T. maritima encodes two proteins, TM1088A and TM1088B.
• These proteins assemble to form the cytosolic component of a putative Trk potassium (K+) transporter.

Purpose of the Study:

• To determine the crystal structure of the TM1088 K+ transporter assembly.
• To elucidate the structural basis of K+ ion transport and gating mechanisms.

Main Methods:

• X-ray crystallography was employed to determine the structure of the TM1088A/TM1088B complex at 3.45 Å resolution.
• High-resolution crystal structures of individual TM1088A (1.50 Å) and TM1088B (1.55 Å) proteins were also determined.

Main Results:

• The crystal structure of the two-subunit TM1088 assembly was solved, revealing a cytosolic gating ring.
• TM1088A and TM1088B proteins are structurally homologous to each other and to other K+ transporters like TrkA.
• The assembly shares significant structural homology and quaternary organization with single-subunit K+ gating rings.

Conclusions:

• The TM1088 structure represents the first structure of a two-subunit Trk assembly.
• This finding provides structural insights into a potential evolutionary ancestor of modern single-subunit K+ gating ring assemblies.
• The study enhances understanding of potassium transporter evolution and function.