Peptide transporters of the proton-dependent oligopeptide transporter (POT) family play a critical role in cellular nutrient uptake by facilitating the translocation of di- and tripeptides across membranes. These transporters rely on the proton motive force to drive substrate influx, providing cells with essential amino acids for protein synthesis and metabolic processes. Among the bacterial POT family members, the dipeptide and tripeptide permease A (DtpA) from Escherichia coli exhibits substrate specificity highly analogous to its human homolog hPEPT1, making it an ideal model system for studying inhibitor modulation. This study investigates how the potent inhibitor Lys[Z-NO2]-Val influences DtpA’s conformational dynamics using single-molecule force spectroscopy (SMFS) under physiologically relevant conditions.
In the absence of inhibitor, DtpA exists in two dominant alternate conformations: one in which transmembrane helix 2 (TMH2) is stabilized (observed in 43% of molecules), and another where TMH2 lacks such stabilization (57% of molecules). These states are interpreted as representing inward-facing and outward-facing conformations, respectively, consistent with the alternating-access mechanism proposed for major facilitator superfamily (MFS) transporters. Upon exposure to increasing concentrations of Lys[Z-NO2]-Val, the proportion of DtpA molecules adopting the stabilized TMH2 conformation rises significantly, reaching 92% at saturation. This shift indicates that inhibitor binding actively promotes a conformational state associated with transport inhibition.
SMFS analysis revealed that Lys[Z-NO2]-Val specifically enhances the stability of interactions within TMH2, without altering the overall strength of other structural interactions. The force peak corresponding to TMH2 unfolding—detected at a contour length of 80 amino acids—showed a marked increase in frequency upon inhibitor addition.1,7-Heptanediol Autophagy This effect was concentration-dependent, demonstrating a clear correlation between inhibitor occupancy and conformational preference. The residues implicated in this interaction include F63, S64, and Y71, all located near the extracellular end of TMH2, suggesting their involvement in ligand recognition and gating regulation.
These findings provide direct evidence that inhibitors can modulate transporter function not by disrupting essential structural elements but by stabilizing specific conformational states that block substrate access. By favoring the inward-facing occluded state, Lys[Z-NO2]-Val effectively locks DtpA in a non-functional configuration, preventing the dynamic transitions required for peptide transport.4-(Triethylsilyl)but-3-yn-1-ol supplier This mechanism highlights the importance of TMH2 as a key regulatory element in the transport cycle and offers insights into rational design of next-generation inhibitors targeting membrane transporters.PMID:33782240
The use of SMFS allowed real-time observation of these conformational changes in intact lipid bilayers, preserving native environmental conditions and enabling detection of subtle differences in mechanical stability. Unlike crystallographic studies, which capture static snapshots often under nonphysiological conditions, SMFS reveals the dynamic equilibrium between functional states. Thus, this approach provides a powerful tool for understanding how small molecules regulate membrane protein function at the single-molecule level.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com