Single-channel water permeabilities of Escherichia coli aquaporins AqpZ and GlpF
Research output: Contribution to journal › Journal article › Research › peer-review
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.
Original language | English |
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Journal | Biophysical Journal |
Volume | 90 |
Issue number | 7 |
Pages (from-to) | 2270-2284 |
Number of pages | 15 |
ISSN | 0006-3495 |
DOIs | |
Publication status | Published - Apr 2006 |
ID: 230978185