Structure-Based Engineering of a Minimal Porin Reveals Loop-Independent Channel Closure

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• 作者：Wolfgang Grosse ; Georgios Psakis ; Barbara Mertins ; Philipp Reiss ; Dirk Windisch ; Felix Brademann ; Jochen B眉rck ; Anne Ulrich ; Ulrich Koert ; Lars-Oliver Essen
• 刊名：Biochemistry
• 出版年：2014
• 出版时间：July 29, 2014
• 年：2014
• 卷：53
• 期：29
• 页码：4826-4838
• 全文大小：963K
• ISSN：1520-4995

文摘

Porins, like outer membrane protein G (OmpG) of Escherichia coli, are ideal templates among ion channels for protein and chemical engineering because of their robustness and simple architecture. OmpG shows fast transitions between open and closed states, which were attributed to loop 6 (L6). As flickering limits single-channel-based applications, we pruned L6 by either 8 or 12 amino acids. While the open probabilities of both L6 variants resemble that of native OmpG, their gating frequencies were reduced by 63 and 81%, respectively. Using the 3.2 脜 structure of the shorter L6 variant in the open state, we engineered a minimal porin (220 amino acids), where all remaining extramembranous loops were truncated. Unexpectedly, this minimized porin still exhibited gating, but it was 5-fold less frequent than in OmpG. The residual gating of the minimal pore is hence independent of L6 rearrangements and involves narrowing of the ion conductance pathway most probably driven by global stretching鈥揻lexing deformations of the membrane-embedded 尾-barrel.