Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Peptides. 2012 Nov;38(1):89-93. doi: 10.1016/j.peptides.2012.08.012. Epub 2012 Aug 23.
Proton-coupled oligopeptide transporters (POTs) utilize the electrochemical proton gradient to facilitate uptake of di- or tripeptide molecules. YjdL is one of four POTs found in Escherichia coli. It has shown an extraordinary preference for di- rather than tripeptides, and is therefore significantly different from prototypical POTs such as the human hPepT1. Nonetheless YjdL contains several highly conserved POT residues, which include Glu388 that is located in the putative substrate binding cavity. Here we present biophysical characterization of WT-YjdL and Glu388Gln. Isothermal titration calorimetrical studies exhibit a K(d) of 14 μM for binding of Ala-Lys to WT-YjdL. Expectedly, no binding could be detected for the tripeptide Ala-Ala-Lys. Surprisingly however, binding could not be detected for Ala-Gln, although earlier studies indicated inhibitory potencies of Ala-Gln to be comparable to Ala-Lys (IC(50) values of 0.6 compared to 0.3mM). Finally, Ala-Lys binding to Glu388Gln was also undetectable which may support a previously suggested role in interaction with the ligand peptide N-terminus.
质子偶联寡肽转运蛋白（POTs）利用电化学质子梯度促进二肽或三肽分子的摄取。YjdL 是大肠杆菌中发现的四种 POTs 之一。它对二肽表现出非凡的偏好，而不是三肽，因此与典型的 POTs（如人类 hPepT1）有很大的不同。尽管如此，YjdL 包含几个高度保守的 POT 残基，其中包括位于假定的底物结合腔内的 Glu388。在这里，我们介绍了 WT-YjdL 和 Glu388Gln 的生物物理特性。等温滴定量热法研究表明，Ala-Lys 与 WT-YjdL 的结合 K(d)为 14 μM。不出所料，三肽 Ala-Ala-Lys 没有检测到结合。然而，令人惊讶的是，Ala-Gln 没有检测到结合，尽管早期的研究表明 Ala-Gln 的抑制作用与 Ala-Lys 相当（IC(50) 值为 0.6 与 0.3mM 相比）。最后，Ala-Lys 与 Glu388Gln 的结合也无法检测到，这可能支持了先前关于与配体肽 N 端相互作用的作用的建议。
