aquaporins

[Kathleen Archer]

Folks,
I don't know about "active" water transport, but aquaporins are channels in
the plasma membrane specifically for the movement of water into or out of
the cell.
For a general introduction see:  http://www.gmm.gu.se/mip-tmr/home.htm
For info on aquaporins in mammals:
http://arbl.cvmbs.colostate.edu/hbooks/molecules/aquaporins.html

Martin Chrispeels has done work with aquaporins in plants and it appears
that in plants at least some of these are gated channels.
Kathleen Archer