ENERGETICS OF GRAMICIDIN HYBRID CHANNEL FORMATION AS A TEST FOR STRUCTURAL EQUIVALENCE - SIDE-CHAIN SUBSTITUTIONS IN THE NATIVE SEQUENCE
ENERGETICS OF GRAMICIDIN HYBRID CHANNEL FORMATION AS A TEST FOR STRUCTURAL EQUIVALENCE - SIDE-CHAIN SUBSTITUTIONS IN THE NATIVE SEQUENCE
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DOI：
10.1016/0022-2836(90)90022-e
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发表时间：
1990-01-05
影响因子：
5.6
通讯作者：
ANDERSEN, OS
中科院分区：
文献类型：
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作者：
DURKIN, JT;KOEPPE, RE;ANDERSEN, OS
为了确定线性短杆菌肽中的氨基酸侧链取代是否改变由修饰的肽形成的跨膜通道的结构，我们已经开发了基于功能（单通道）测量的短杆菌肽通道之间的肽骨架的结构等效性的定量测量。实验利用短杆菌肽通道是对称二聚体的事实，并且由不同短杆菌肽类似物形成的通道可以根据其单通道电流幅度或持续时间来区分。由此可以确定在化学上不同的肽之间是否可以形成杂交通道，即肽是否可以彼此适应。此外，由于通道形成的相对速率以及纯通道和混合通道类型的相对浓度可以在相同的膜中测量，这些实验提供了混合通道形成相对于纯通道形成的能量成本的定量测量。对于各种各样的不同的侧链，我们发现，在位置1处，在跨膜二聚体中的两个单体之间的连接处，如甘氨酸至苯丙氨酸的极端取代不会引起通道形成的能量成本，这意味着由每个修饰的肽形成的通道在结构上是等效的。此外，平均持续时间的混合通道（除了那些具有酪氨酸或六氟缬氨酸在位置1）是中间的平均持续时间的各个纯通道类型，从而提供了进一步的证据，由序列取代短杆菌肽形成的通道之间的结构等效性。
To determine whether amino acid side-chain substitutions in linear gramicidins alter the structure of membrane-spanning channels formed by the modified peptides, we have developed a quantitative measure of structural equivalence of the peptide backbone among gramicidin channels based on functional (single-channel) measurements. The experiments exploit the fact that gramicidin channels are symmetrical dimers, and that channels formed by different gramicidin analogues can be distinguished on the basis of their single-channel current amplitudes or durations. It is thereby possible to determine whether hybrid channels can form between chemically dissimilar peptides, i.e. whether the peptides can adapt to each other. Further since the relative rates of channel formation as well as the relative concentrations of pure and hybrid channel types can be measured in the same membrane, these experiments provide a quantitative measure of the energetic cost of hybrid channel formation relative to the formation of the pure channels. For a wide variety of different side-chains, we find that substitutions as extreme as glycine to phenylalanine at position 1, at the join between the two monomers in a membrane-spanning dimer, incur no energetic cost for channel formation, which implies that channels formed by each of the modified peptides are structurally equivalent. In addition, the average durations of the hybrid channels (except those having tyrosine or hexafluorovaline at position 1) are intermediate to the average durations of the respective pure channel types, thus providing further evidence for structural equivalence among channels formed by sequence-substituted gramicidins.