TY - JOUR
T1 - Single-channel water permeabilities of Escherichia coli aquaporins AqpZ and GlpF
AU - Jensen, Morten
AU - Mouritsen, Ole G.
PY - 2006/4
Y1 - 2006/4
N2 - From equilibrium molecular dynamics simulations we have determined single-channel water permeabilities for Escherichia coli aquaporin Z (AqpZ) and aquaglyceroporin GlpF with the channels embedded in lipid bilayers. GlpF's osmotic water permeability constant pf exceeds by 2-3 times that of AqpZ and the diffusive permeability constant (pd) of GlpF is found to exceed that of AqpZ 2-9-fold. Achieving complete water selectivity in AqpZ consequently implies lower transport rates overall relative to the less selective, wider channel of GlpF. For AqpZ, the ratio pf/pd ≅ 12 is close to the average number of water molecules in the channel lumen, whereas for GlpF, pf/pd ≅ 4. This implies that single-file structure of the luminal water is more pronounced for AqpZ, the narrower channel of the two. Electrostatics profiles across the pore lumens reveal that AqpZ significantly reinforces water-channel interactions, and weaker water-water interactions in turn suppress water-water correlations relative to GlpF. Consequently, suppressed water-water correlations across the narrow selectivity filter become a key structural determinant for water permeation causing luminal water to permeate slower across AqpZ.
AB - From equilibrium molecular dynamics simulations we have determined single-channel water permeabilities for Escherichia coli aquaporin Z (AqpZ) and aquaglyceroporin GlpF with the channels embedded in lipid bilayers. GlpF's osmotic water permeability constant pf exceeds by 2-3 times that of AqpZ and the diffusive permeability constant (pd) of GlpF is found to exceed that of AqpZ 2-9-fold. Achieving complete water selectivity in AqpZ consequently implies lower transport rates overall relative to the less selective, wider channel of GlpF. For AqpZ, the ratio pf/pd ≅ 12 is close to the average number of water molecules in the channel lumen, whereas for GlpF, pf/pd ≅ 4. This implies that single-file structure of the luminal water is more pronounced for AqpZ, the narrower channel of the two. Electrostatics profiles across the pore lumens reveal that AqpZ significantly reinforces water-channel interactions, and weaker water-water interactions in turn suppress water-water correlations relative to GlpF. Consequently, suppressed water-water correlations across the narrow selectivity filter become a key structural determinant for water permeation causing luminal water to permeate slower across AqpZ.
UR - http://www.scopus.com/inward/record.url?scp=33646251373&partnerID=8YFLogxK
U2 - 10.1529/biophysj.105.073965
DO - 10.1529/biophysj.105.073965
M3 - Journal article
C2 - 16399837
AN - SCOPUS:33646251373
SN - 0523-6800
VL - 90
SP - 2270
EP - 2284
JO - Biophysical Society. Annual Meeting. Abstracts
JF - Biophysical Society. Annual Meeting. Abstracts
IS - 7
ER -