Sung S S, Jordan P C
Department of Chemistry, Brandeis University, Waltham, Massachusetts 02254.
Biophys J. 1988 Sep;54(3):519-26. doi: 10.1016/S0006-3495(88)82984-9.
Recent experimental studies by Durkin, J. T., O. S. Andersen, F. Heitz, Y. Trudelle, and R. E. Koeppe II (1987. Biophys. J. 51:451a) have suggested that the antiparallel double-stranded helical (APDS) dimer of gramicidin can form a transmembrane cation channel. This article reports a theoretical study that successfully rationalizes the channel properties of the APDS dimer. As in the case of the head-to-head (HH) dimer, the APDS exhibits a high potential energy barrier as anions approach the channel mouth, according for the observation of valence selectivity. The calculated potential energies of cations show two binding sites near the channel mouths, a typical feature of the HH channel. The potential energies of hydrated cations in the APDS are generally higher than those in the HH channel and show a larger pseudoperiodicity and higher barriers, an observation which suggests that the APDS should exhibit lower single channel conductance.
杜尔金、J.T.、O.S. 安德森、F. 海茨、Y. 特鲁德尔和R.E. 科佩二世（1987年，《生物物理学杂志》第51卷：451a）近期的实验研究表明，短杆菌肽的反平行双链螺旋（APDS）二聚体可形成跨膜阳离子通道。本文报道了一项理论研究，该研究成功地解释了APDS二聚体的通道特性。与头对头（HH）二聚体的情况一样，当阴离子接近通道口时，APDS表现出高势能垒，这与价态选择性的观察结果相符。计算得出的阳离子势能显示在通道口附近有两个结合位点，这是HH通道的一个典型特征。APDS中水合阳离子的势能通常高于HH通道中的势能，并且显示出更大的伪周期性和更高的势垒，这一观察结果表明APDS应表现出较低的单通道电导。
