Porin from Rhodobacter capsulatus
PDB ID: 2por
Theory
Gram-negative bacteria protect themselves from hostile environments by an outer membrane. This membrane, however, has to be permeable to polar, low molecular mass solutes including nutrients. For this purpose it contains channel-forming proteins called porins, which are usually trimeric with relative subunit masses between 30 and 50 kDa. Typical exclusion limits are around 600 daltons. Porins are quite resistant to denaturation by heat or detergents.
We solved the structure of the porin from R.capsulatus in 1989 to 6 A resolution. With a different crystal form the model could be refined to 1.8 A in 1992. Unlike most other integral membrane proteins, which are essentially alpha-helical, the porin consists predominantly of beta-sheet structures.
The integral membrane protein porin from R.capsulatus consists of three tightly associated 16-stranded beta-barrels that give rise to three distinct diffusion channels for small solutes through the outer membrane. The X-ray structure of this porin has revealed details of its shape, the residue distributions within the pore and at the membrane-facing surface, and the location of the calcium sites. The electrostatic potential has been calculated and related to function. Moreover, potential calculations were found to predict the Ca2+ sites.
Related Articles:
Weiss, M.S., Nestel, U., Wacker, T., Weckesser, J., Kreutz, W., Welte, W. & Schulz, G.E. (1989). The crystal structure of porin from Rhodobacter capsulatus at 6 Å resolution. FEBS Lett. 256, 143-146.
Weiss, M.S., Wacker, T., Weckesser, J., Welte, W. & Schulz, G.E. (1990). The three-dimensional structure of porin from Rhodobacter capsulatus at 3 Å resolution. FEBS Lett. 267, 268-272.
Weiss, M.S., Kreusch, A., Schiltz, E., Nestel, U., Welte, W., Weckesser, J. & Schulz, G.E. (1991). The structure of porin from Rhodobacter capsulatus at 1.8 Å resolution. FEBS Lett. 280, 379-382.
Weiss, M.S., Abele, U., Weckesser, J., Welte, W., Schiltz, E. & Schulz, G.E. (1991). Molecular architecture and electrostatic properties of a bacterial porin. Science 254, 1627-1630.
Welte, W., Weiss, M.S., Nestel, U., Weckesser, J., Schiltz, E. & Schulz, G.E. (1991). Prediction of the general structure of OmpF and PhoE from the sequence and structure of porin from Rhodobacter capsulatus. Orientation of porin in the membrane. Biochim. Biophys. Acta 1080, 271-274.
Weiss, M.S. & Schulz, G.E. (1992). Structure of porin refined at 1.8 Å resolution. J. Mol. Biol. 227, 493-509.
Schulz, G.E. (1993). Bacterial porins: structure and function. Curr. Opin. Cell Biol. 5, 701-707.
Weiss, M.S. & Schulz, G.E. (1993). Porin conformation in the absence of calcium; refined structure at 2.5 Å resolut
Theory
Gram-negative bacteria protect themselves from hostile environments by an outer membrane. This membrane, however, has to be permeable to polar, low molecular mass solutes including nutrients. For this purpose it contains channel-forming proteins called porins, which are usually trimeric with relative subunit masses between 30 and 50 kDa. Typical exclusion limits are around 600 daltons. Porins are quite resistant to denaturation by heat or detergents.
We solved the structure of the porin from R.capsulatus in 1989 to 6 A resolution. With a different crystal form the model could be refined to 1.8 A in 1992. Unlike most other integral membrane proteins, which are essentially alpha-helical, the porin consists predominantly of beta-sheet structures.
The integral membrane protein porin from R.capsulatus consists of three tightly associated 16-stranded beta-barrels that give rise to three distinct diffusion channels for small solutes through the outer membrane. The X-ray structure of this porin has revealed details of its shape, the residue distributions within the pore and at the membrane-facing surface, and the location of the calcium sites. The electrostatic potential has been calculated and related to function. Moreover, potential calculations were found to predict the Ca2+ sites.
Related Articles:
Weiss, M.S., Nestel, U., Wacker, T., Weckesser, J., Kreutz, W., Welte, W. & Schulz, G.E. (1989). The crystal structure of porin from Rhodobacter capsulatus at 6 Å resolution. FEBS Lett. 256, 143-146.
Weiss, M.S., Wacker, T., Weckesser, J., Welte, W. & Schulz, G.E. (1990). The three-dimensional structure of porin from Rhodobacter capsulatus at 3 Å resolution. FEBS Lett. 267, 268-272.
Weiss, M.S., Kreusch, A., Schiltz, E., Nestel, U., Welte, W., Weckesser, J. & Schulz, G.E. (1991). The structure of porin from Rhodobacter capsulatus at 1.8 Å resolution. FEBS Lett. 280, 379-382.
Weiss, M.S., Abele, U., Weckesser, J., Welte, W., Schiltz, E. & Schulz, G.E. (1991). Molecular architecture and electrostatic properties of a bacterial porin. Science 254, 1627-1630.
Welte, W., Weiss, M.S., Nestel, U., Weckesser, J., Schiltz, E. & Schulz, G.E. (1991). Prediction of the general structure of OmpF and PhoE from the sequence and structure of porin from Rhodobacter capsulatus. Orientation of porin in the membrane. Biochim. Biophys. Acta 1080, 271-274.
Weiss, M.S. & Schulz, G.E. (1992). Structure of porin refined at 1.8 Å resolution. J. Mol. Biol. 227, 493-509.
Schulz, G.E. (1993). Bacterial porins: structure and function. Curr. Opin. Cell Biol. 5, 701-707.
Weiss, M.S. & Schulz, G.E. (1993). Porin conformation in the absence of calcium; refined structure at 2.5 Å resolut