Gain of function mutations in membrane region M2C2 of KtrB open a gate controlling K+ transport by the KtrAB system from Vibrio alginolyticus.

The Journal of Biological Chemistry
Inga HäneltEvert P Bakker

Abstract

KtrB, the K(+)-translocating subunit of the Na(+)-dependent bacterial K(+) uptake system KtrAB, consists of four M(1)PM(2) domains, in which M(1) and M(2) are transmembrane helices and P indicates a p-loop that folds back from the external medium into the cell membrane. The transmembrane stretch M(2C) is, with its 40 residues, unusually long. It consists of three parts, the hydrophobic helices M(2C1) and M(2C3), which are connected by a nonhelical M(2C2) region, containing conserved glycine, alanine, serine, threonine, and lysine residues. Several point mutations in M(2C2) led to a huge gain of function of K(+) uptake by KtrB from the bacterium Vibrio alginolyticus. This effect was exclusively due to an increase in V(max) for K(+) transport. Na(+) translocation by KtrB was not affected. Partial to complete deletions of M(2C2) also led to enhanced V(max) values for K(+) uptake via KtrB. However, several deletion variants also exhibited higher K(m) values for K(+) uptake and at least one deletion variant, KtrB(Delta326-328), also transported Na(+) faster. The presence of KtrA did not suppress any of these effects. For the deletion variants, this was due to a diminished binding of KtrA to KtrB. PhoA studies indicated that M(2C2) f...Continue Reading

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Citations

Feb 15, 2011·Nature·Yu CaoMing Zhou
Dec 29, 2010·Proceedings of the National Academy of Sciences of the United States of America·Somshuvra Mukhopadhyay, Adam D Linstedt
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Oct 1, 2011·The FEBS Journal·Ingo Dreyer, Nobuyuki Uozumi
Jul 11, 2014·Current Opinion in Structural Biology·Elena J Levin, Ming Zhou
Dec 22, 2014·Current Opinion in Biotechnology·Shin HamamotoNobuyuki Uozumi
Jun 14, 2014·Frontiers in Microbiology·Bonnie K BaxterAharon Oren
Jun 22, 2017·Nature·Ching-Shin HuangDavid L Stokes
Apr 20, 2013·Nature·Ricardo S Vieira-PiresJoão H Morais-Cabral
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