Structure of the membrane channel porin from Rhodopseudomonas blastica at 2.0 A resolution.
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Kreusch A, Neubuser A, Schiltz E, Weckesser J, Schulz GE
Structure of the membrane channel porin from Rhodopseudomonas blastica at 2.0 A resolution.
Protein Sci. 1994 Jan;3(1):58-63.
- PubMed ID
- 8142898 [ View in PubMed]
- Abstract
The crystal structure of a membrane channel, homotrimeric porin from Rhodopseudomonas blastica has been determined at 2.0 A 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.