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Voltage and pH-induced channel closure of porin OmpF visualized by atomic force microscopy
Journal
Journal of molecular biology
Volume
285
Number
4
Pages / Article-Number
1347-51
Keywords
atomic force microscopy, conformation change, Escherichia coli porin OmpF, voltage gating
Abstract
Gram-negative bacteria are protected by an outer membrane in which trimeric channels, the porins, facilitate the passage of small solutes. The pores are formed by membrane-spanning antiparallel beta-strands, which are connected by short turns on the periplasmic side and long loops on the extracellular side. Voltage and pH-dependent conformational changes of these extracellular loops have now been visualized by atomic force microscopy of two-dimensional crystals of Escherichia coli porin OmpF. The observed conformational changes accompany the closure of the channel entrance, and suggest that this is a mechanism that the cells have evolved to protect themselves from drastic changes of the environment.
