Structure comparisons of closed aquaporins from P. pastoris and spinach.

(A) Comparison of the Aqy1 from P. pastoris (left panel) with the spinach aquaporin SoPIP2;1 (right panel) shown as HOLE representation. The pore is occluded by the N terminus in Aqy1, and by loop D in SoPIP2;1. (B) The pore diameter of closed Aqy1 (yellow), closed SoPIP2;1 (green), and constitutively open bAQP1 (black) structures calculated with program HOLE. (C) Stereo-view of the superposition of SoPIP2;1 (green) onto Aqy1 (yellow). Residues identified in the narrowest parts of the pores of the respective aquaporin are shown in stick representation.