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Updated: Jun 21, 2026

From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins
Published on: July 4, 2016
Crystal structure of a periplasmic substrate-binding protein in complex with calcium lactate
Nobuhiko Akiyama1, Kazuki Takeda, Kunio Miki
1Department of Chemistry, Kyoto University, Sakyo-ku, Japan.
Abstract:
Lactate is utilized in many biological processes, and its transport across biological membranes is mediated with various types of transporters. Here, we report the crystal structures of a lactate-binding protein of a TRAP (tripartite ATP-independent periplasmic) secondary transporter from Thermus thermophilus HB8. The folding of the protein is typical for a type II periplasmic solute-binding protein and forms a dimer in a back-to-back manner. One molecule of l-lactate is clearly identified in a cleft of the protein as a complex with a calcium ion. Detailed crystallographic and biochemical analyses revealed that the calcium ion can be removed from the protein and replaced with other divalent cations. This characterization of the structure of a protein binding with calcium lactate makes a significant contribution to our understanding of the mechanisms by which calcium and lactate are accommodated in cells.
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