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 (OR52_cs), 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 OR52_cs to mimic that of OR52E8. The resulting engineered receptor, OR52_cs^E8pocket, recapitulates OR52E8 odorant specificity, including chiral selectivity for the (R)-HMHA enantiomer. We determined the cryo-EM structure of the HMHA-OR52_cs^E8pocket-G_s 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 N^5×42, 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.