Design and characterization of a constitutively open KcsA.
The molecular nature of the structure responsible for proton sensitivity in KcsA has been identified as a charge cluster that surrounds the inner helical bundle gate. Here, we show that this proton sensor can be modified to engineer a constitutively open form of KcsA, amenable to functional, spectroscopic and structural analyses. By combining charge neutralizations for all acidic and basic residues in the cluster at positions 25, 117-122 and 124 (but not E118), a mutant KcsA is generated that displays constitutively open channel activity up to pH 9. The structure of this mutant revealed that full opening appears to be inhibited by lattice forces since the activation gate seems to be only on the early stages of opening.
Cuello
Luis G
LG
Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
Jogini
Vishwanath
V
Cortes
D Marien
DM
Sompornpisut
Amornrat
A
Purdy
Michael D
MD
Wiener
Michael C
MC
Perozo
Eduardo
E
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D015640:Ion Channel Gating / Q000235:genetics*; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011487:Protein Conformation; D015202:Protein Engineering; D040681:Structural Homology, Protein
D001426:Bacterial Proteins; D050505:Mutant Proteins; D015221:Potassium Channels; C107790:prokaryotic potassium channel