| Description | The Trk system is a low to medium affinity potassium uptake system, widely found in both in bacteria and archaea, where the uptake of K(+) is believed to be linked to H(+) symport [ ]. The core Trk system consists of two proteins, the integral membrane K(+)-translocating protein TrkH (or TrkG), and the regulatory NAD-binding peripheral membrane protein TrkA [, , ]. In Escherichia coli the activity of TrkH is dependent on the ATP-binding protein SapD (also known as TrkE) which is part of the SapABCDF ABC transporter, involved in putrescine export []. Not all Trk systems are dependent on SapD however -it is thought that these may utilise ATP-binding proteins from other ABC transporters [].Sequence analysis of TrkA reveals that the protein consists of 2 tandemly arrayed halves that are 22% identical, a situation that might have arisen through gene duplication. TrkA also exhibits similarity to other Escherichia coli proteins [ ], in particular KefC, a glutathione- regulated efflux protein [], and to various dehydrogenase proteins that possess NAD+binding sites. TrkA plays a regulatory role on TrkH gating. TrkA, binds ADP in its N2 domain to form a tetrameric ring which closes the channel. When ATP is bound to N1 and N2 domains of TrkA, it induces a tetramer-to-dimer conversion which opens TrkH [ ]. | Name | Potassium uptake protein TrkA |
| Short Name | K_uptake_TrkA | Type | Family |
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