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Ion channel formation by zervamicin-IIB (1993)

Sansom, M. S. P. ; Balaram, P. ; Karle, I. L.

Springer

European biophysics journal 21 (1993), S. 369-383

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ISSN: 1432-1017

Keywords: Ion channel ; Peptaibol ; Molecular modelling ; Channel-forming peptide

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Physics

Notes: Abstract Zervamicin-IIB (Zrv-IIB) is a 16 residue peptaibol which forms voltage-activated, multiple conductance level channels in planar lipid bilayers. A molecular model of Zrv-IIB channels is presented. The structure of monomerc Zrv-II3 is based upon the crystal structure of Zervamicin-Leu. The helical backbone is kinked by a hydroxyproline residue at position 10. Zrv-IIB channels are modelled as helix bundles of from 4 to 8 parallel helices surrounding a central pore. The monomers are packed with their C-terminal helical segments in close contact, and the bundles are stabilized by hydrogen bonds between glutamine 11 and hydroxyproline 10 of adjacent helices. Interaction energy profiles for movement of three different probes species (K+, Cl− and water) through the central pore are analyzed. The conformations of: (a) the sidechain of glutamine 3; (b) the hydroxyl group of hydroxyproline 10; and (c) the C-terminal hydroxyl group are “optimized” in order to maximize favourable interactions between the channel and the probes, resulting in favourable interaction energy profiles for all three. This suggests that conformational flexibility of polar sidechains enables the channel lining to mimic an aqueous environment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00185864

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Apolar peptide models for conformational heterogeneity, hydration, and packing of polypeptide helices: Crystal structure of hepta- and octapeptides containing α-aminoisobutyric acid (1990)

Karle, Isabella L. ; Flippen-Anderson, Judith L. ; Uma, K. ; [et al.]

New York, NY : Wiley-Blackwell

Proteins: Structure, Function, and Genetics 7 (1990), S. 62-73

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ISSN: 0887-3585

Keywords: hydrophobic α-helices ; water insertion into helix ; water in hydrophobic pocket ; helix unfolding ; helix folding ; parallel packing ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine

Notes: The crystal structures of two helical peptides Boc-Val-Ala-Leu-Aib-Val-Ala-Leu-OMe (VALU-7) and Boc-Val-Ala-Leu-Aib-Val-Ala-Leu-Aib-OMe (VALU-8) have been determined to a resolution of 1.0 and 0.9 Å, respectively. Both the seven and eight residue peptides crystallize with two conformers per asymmetric unit. The VALU-8 conformers are completely helical and differ only at the C-terminus by a sign reversal of the φ, ψ angles of the last residue. One of the VALUE-7 conformers occurs as a normal α-helix, whereas in the other, the N(7)=O(3) α-type hydrogen bond is ruptured by the entry of a water molecule (W) into the helix, which in turn makes hydrogen bonds N(7)⃛W = 2.97 Å and ⃛O(3) = 2.77 Å. The other side of the water molecule is surrounded by a hydrophobic pocket. These two conformers give a static representation of a step in a possible helix unwinding or folding process. In the value-8 crystal the helices aggregate in a parallel mode, whereas the aggregation is antiparallel in the VALU-7 crystal. The crystal parameters are VALUE-7 crystal. The crystal parameters are VALUE-7, P21, a = 10.203 (3) Å, b = 19.744 (6) Å, c = 22.561 (6) Å, α = 96.76°, Z = 4, C38, H69N7O10·0.5 H2O, R = 6.65% for 3674 reflections observed 〉3σ(F): and VALU-8, P21, a; = 10.596 (4) Å, b = 27.57 (6) Å, c = 17.745 (5) Å, β = 95.76 (3)°, Z = 4, C42H76N76O11·0.25 CH3OH, R = 6.63% for 4701 reflections observed 〉3σ(F).

Additional Material: 4 Ill.