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Structure of the membrane channel porin from Rhodopseudomonas blastica at 2.0 Å resolution
Author(s) -
Kreusch A.,
Neubüser A.,
Schiltz E.,
Weckesser J.,
Schulz G.E.
Publication year - 1994
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560030108
Subject(s) - porin , crystallography , chemistry , membrane , resolution (logic) , protein subunit , molecule , side chain , stereochemistry , protein structure , biophysics , bacterial outer membrane , biology , biochemistry , organic chemistry , escherichia coli , artificial intelligence , computer science , gene , polymer
The crystal structure of a membrane channel, homotrimeric porin from Rhodopseudomonas blastica has been determined at 2.0 Å resolution by multiple isomorphous replacement and structural refinement. The current model has an R ‐factor of 16.5% and consists of 289 amino acids, 238 water molecules, and 3 detergent molecules per subunit. The partial protein sequence and subsequently the complete DNA sequence were determined. The general architecture is similar to those of the structurally known porins. As a particular feature there are 3 adjacent binding sites for n ‐alkyl chains at the molecular 3‐fold axis. The side chain arrangement in the channel indicates a transverse electric field across each of the 3 pore eyelets, which may explain the discrimination against nonpolar solutes. Moreover, there are 2 significantly ordered girdles of aromatic residues at the nonpolar/polar borderlines of the interface between protein and membrane. Possibly, these residues shield the polypeptide conformation against adverse membrane fluctuations.