A water channel of the nematode C. elegans and its implications for channel selectivity of MIP proteins.
A genome project focusing on the nematode Caenorhabditis elegans has demonstrated the presence of eight cDNAs belonging to the major intrinsic protein superfamily. We functionally characterized one of these cDNAs named C01G6.1. Injection of C01G6.1 cRNA increased the osmotic water permeability (Pf) of Xenopus oocytes 11-fold and the urea permeability 4.5-fold but failed to increase the glycerol permeability. It has been speculated that the MIP family may be separated into two large subfamilies based on the presence or absence of two segments of extra amino acid residues ( approximately 15 amino acids) at the second and third extracellular loops. Because C01G6.1 (designated AQP-CE1), AQP3, and glycerol facilitator (GlpF) all have these two segments, we replaced the segments of AQP-CE1 with those of AQP3 and GlpF to identify their roles. The functional characteristics of these mutants were principally similar to that of wild-type AQP-CE1, although the values of Pf and urea permeability were decreased by 39-74% and 28-65%, respectively. These results suggest that the two segments of extra amino acid residues may not contribute to channel selectivity or formation of the route for small solutes.
Kuwahara
M
M
Second Department of Internal Medicine, School of Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Ishibashi
K
K
Gu
Y
Y
Terada
Y
Y
Kohara
Y
Y
Marumo
F
F
Sasaki
S
S
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D051398:Aquaporin 1; D051400:Aquaporin 3; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins; D029968:Escherichia coli Proteins; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009865:Oocytes / Q000378:metabolism; D009995:Osmosis / Q000502:physiology; D010539:Permeability; D014508:Urea / Q000493:pharmacokinetics; D014867:Water / Q000378:metabolism; D014982:Xenopus laevis
D020346:Aquaporins; D001425:Bacterial Outer Membrane Proteins; D029742:Caenorhabditis elegans Proteins; D029968:Escherichia coli Proteins; D005136:Eye Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C116823:aqp-1 protein, C elegans; C030328:aquaporin 0; D014867:Water; C078043:GlpF protein, E coli; D051398:Aquaporin 1; D051400:Aquaporin 3; D014508:Urea