Structural basis of the sweat odorant HMHA recognition by the human odorant receptor OR52E8

3-Hydroxy-3-methyl hexanoic acid (HMHA), a key component of human axillary sweat, specifically activates the human odorant receptor OR52E8. However, the molecular basis of this recognition remains elusive. A recent structural study of an odorant-bound consensus OR52 (OR52cs), a representative of the OR52 family, suggested the molecular mechanism for carboxylic acid odorant recognition. Because native OR52E8 exhibits low surface expression, hindering structural analysis, we engineered the odorant-binding pocket of OR52cs to mimic that of OR52E8. The resulting engineered receptor, OR52csE8pocket, recapitulates OR52E8 odorant specificity, including chiral selectivity for the (R)-HMHA enantiomer. We determined the cryo-EM structure of the HMHA–OR52csE8pocket–Gs complex, revealing the HMHA binding pocket and enabling structure-guided interpretation of receptor specificity. The C3 hydroxyl branch of HMHA, essential for OR52E8 activation, forms a polar interaction with N5×42, a residue unique to OR52E8 within the OR52 family. The C3 methyl group, important for enantiomer-specific HMHA recognition, interacts with residues in TM3 and TM6. We further identified natural OR52E8 variants with altered responses to HMHA, which may underlie inter-individual differences in HMHA sensitivity and perception. Together, our findings suggest the molecular determinants of OR52E8 specificity and provide molecular insights into the genetic variability in human body odor perception. Cryo-EM analysis of an engineered consensus receptor mimicking the human odorant receptor OR52E8 reveals how this receptor recognizes HMHA, a major component of axillary sweat, and shows how natural receptor variants may explain individual differences in human body odor perception.