Part of the tripartite ATP-independent periplasmic (TRAP) transport system TakPQM involved in the uptake of alpha-keto acids. This protein specifically binds alpha-keto acids including pyruvate, oxobutyrate, oxovalerate and 4-methyl-2-oxovalerate. Ligand-binding affinity increases with the increasing chain length of the aliphatic backbone of the ligand. Is not able to bind alpha-ketoglutarate. Homodimer. The complex comprises the extracytoplasmic solute receptor protein TakP, and the two transmembrane proteins TakQ and TakM. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Belongs to the bacterial solute-binding protein 7 family. Was originally (Ref.1) annotated as coding for a sorbitol/mannitol-binding protein based solely on its position in the genome close to the smo operon encoding known sorbitol/mannitol catabolic genes.