Helix dipoles

Nicholson, H., Becktel, W.J., Matthews, B.W. Enhanced protein thermostability from designed mutations that interact with a-helix dipoles. Nature 336 651-656, 1988. 

Mattliew, M. K., and Balaram, A., 1983. A helix dipole model for alamedii-cin and related tran.smembrane channels. FEES Letters 157 1-5. 

N-eap helix dipole salt bridge salt bridge extra helix helix dipole C-cap stabili ation stability stabiiization... 

Warwicker, J. Watson, H., Calculation of the electrostatic potential in the active site cleft due to a helix dipoles, J. Mol. Biol. 1982,157, 671-679... 

E. Galoppini, M. A. Fox, Effect of the Electric Field Generated by the Helix Dipole on Photoinduced Intramolecular Electron Transfer in Dichromophoric Alpha-Hdical Peptides , J. Am. Chem. Soc 1996, 118, 2299-2300. 

W. G. J. Hoi, The role of the a-helix dipole in protein function and structure, Prog. Biophys. 

Fig. 12. Reaction mechanism of oxaldie 1 catalyzed decarboxylation of oxaloacetate.The organization of several flanking lysine residues depresses the plC of the catalytically active Lys side chain. The free amino terminal of the folded peptide is the most reactive residue because its plC is depressed by the positive end of the helix dipole...

Calabrese JC, Jordan DB, Boodhoo A, Sariaslani S, Vannelli T (2004) Crystal structure of phenylalanine ammonia lyase multiple helix dipoles implicated in catalysis. Biochemistry 43(36) 11403-11416... 

Fig. 8. An example of the lack of strong interaction between Ca ions bound to proteins and a-helix dipoles. Shown is the double-Ca -binding site of thermolysin (3TLN), with two associated helices (residues Gly-136 to Asn-181). Side chains are drawn only for Asp-138 and Glu-177 (thick lines), two Ca -ligand residues from the helical regions. Only main-chain atoms are shown for other residues. The Ca ions are circles. The positive amino terminus of the dipole from the first helix passes to one side of the Ca positions. The negative carboxy terminus of the dipole from the second helix bypasses the Ca positions at some distance. The only interaction between the ions and the helices is with the side chains of Asp-138 and Glu-177 that protrude from their respective helix axes.

Sali, D., Bycroft, M. and Fersht, A.R. (1988) Stabilization of protein stractnre by of interaction of dr-helix dipole with a charged side chain. Nature, 335, 740-743. 

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