1e54
From Proteopedia
(New page: 200px<br /><applet load="1e54" size="450" color="white" frame="true" align="right" spinBox="true" caption="1e54, resolution 2.1Å" /> '''ANION-SELECTIVE PORIN...) |
|||
| Line 1: | Line 1: | ||
| - | [[Image:1e54.gif|left|200px]]<br /><applet load="1e54" size=" | + | [[Image:1e54.gif|left|200px]]<br /><applet load="1e54" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1e54, resolution 2.1Å" /> | caption="1e54, resolution 2.1Å" /> | ||
'''ANION-SELECTIVE PORIN FROM COMAMONAS ACIDOVORANS'''<br /> | '''ANION-SELECTIVE PORIN FROM COMAMONAS ACIDOVORANS'''<br /> | ||
==Overview== | ==Overview== | ||
| - | BACKGROUND: Porins provide diffusion channels for salts and small organic | + | BACKGROUND: Porins provide diffusion channels for salts and small organic molecules in the outer membrane of bacteria. In OmpF from Escherichia coli and related porins, an electrostatic field across the channel and a potential, originating from a surplus of negative charges, create moderate cation selectivity. Here, we investigate the strongly anion-selective porin Omp32 from Comamonas acidovorans, which is closely homologous to the porins of pathogenic Bordetella and Neisseria species. RESULTS: The crystal structure of Omp32 was determined to a resolution of 2.1 A using single isomorphous replacement with anomalous scattering (SIRAS). The porin consists of a 16-stranded beta barrel with eight external loops and seven periplasmic turns. Loops 3 and 8, together with a protrusion located within beta-strand 2, narrow the cross-section of the pore considerably. Arginine residues create a charge filter in the constriction zone and a positive surface potential at the external and periplasmic faces. One sulfate ion was bound to Arg38 in the channel constriction zone. A peptide of 5.8 kDa appeared bound to Omp32 in a 1:1 stoichiometry on the periplasmic side close to the symmetry axis of the trimer. Eight amino acids of this peptide could be identified, revealing specific interactions with beta-strand 1 of the porin. CONCLUSIONS: The Omp32 structure explains the strong anion selectivity of this porin. Selectivity is conferred by a positive potential, which is not attenuated by negative charges inside the channel, and by an extremely narrow constriction zone. Moreover, Omp32 represents the anchor molecule for a peptide which is homologous to proteins that link the outer membrane to the cell wall peptidoglycan. |
==About this Structure== | ==About this Structure== | ||
| - | 1E54 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Delftia_acidovorans Delftia acidovorans] with CA and SO4 as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | + | 1E54 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Delftia_acidovorans Delftia acidovorans] with <scene name='pdbligand=CA:'>CA</scene> and <scene name='pdbligand=SO4:'>SO4</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1E54 OCA]. |
==Reference== | ==Reference== | ||
| Line 24: | Line 24: | ||
[[Category: outer membrane protein]] | [[Category: outer membrane protein]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:23:59 2008'' |
Revision as of 10:23, 21 February 2008
|
ANION-SELECTIVE PORIN FROM COMAMONAS ACIDOVORANS
Overview
BACKGROUND: Porins provide diffusion channels for salts and small organic molecules in the outer membrane of bacteria. In OmpF from Escherichia coli and related porins, an electrostatic field across the channel and a potential, originating from a surplus of negative charges, create moderate cation selectivity. Here, we investigate the strongly anion-selective porin Omp32 from Comamonas acidovorans, which is closely homologous to the porins of pathogenic Bordetella and Neisseria species. RESULTS: The crystal structure of Omp32 was determined to a resolution of 2.1 A using single isomorphous replacement with anomalous scattering (SIRAS). The porin consists of a 16-stranded beta barrel with eight external loops and seven periplasmic turns. Loops 3 and 8, together with a protrusion located within beta-strand 2, narrow the cross-section of the pore considerably. Arginine residues create a charge filter in the constriction zone and a positive surface potential at the external and periplasmic faces. One sulfate ion was bound to Arg38 in the channel constriction zone. A peptide of 5.8 kDa appeared bound to Omp32 in a 1:1 stoichiometry on the periplasmic side close to the symmetry axis of the trimer. Eight amino acids of this peptide could be identified, revealing specific interactions with beta-strand 1 of the porin. CONCLUSIONS: The Omp32 structure explains the strong anion selectivity of this porin. Selectivity is conferred by a positive potential, which is not attenuated by negative charges inside the channel, and by an extremely narrow constriction zone. Moreover, Omp32 represents the anchor molecule for a peptide which is homologous to proteins that link the outer membrane to the cell wall peptidoglycan.
About this Structure
1E54 is a Protein complex structure of sequences from Delftia acidovorans with and as ligands. Full crystallographic information is available from OCA.
Reference
Crystal structure of Omp32, the anion-selective porin from Comamonas acidovorans, in complex with a periplasmic peptide at 2.1 A resolution., Zeth K, Diederichs K, Welte W, Engelhardt H, Structure. 2000 Sep 15;8(9):981-92. PMID:10986465
Page seeded by OCA on Thu Feb 21 12:23:59 2008
