Mechanism of the conformational transition of melittin.

It is known that, while melittin at micromolar concentrations is unfolded under conditions of low ionic strength at neutral pH, it adopts a tetrameric alpha-helical structure under conditions of high ionic strength, at alkaline pH, or at high peptide concentrations. To understand the mechanism of the conformational transition of melittin, we examined in detail the conformation of melittin under various conditions by far-UV circular dichroism at 20 degrees C. We found that the helical conformation is also stabilized by strong acids such as perchloric acid. The effects of various acids varied largely and were similar to those of the corresponding salts, indicating that the anions are responsible for the salt- or acid-induced transitions. The order of effectiveness of various monovalent anions was consistent with the electroselectivity series of anions toward anion-exchange resins, indicating that the anion binding is responsible for the salt- or acid-induced transitions. From the NaCl-, HCl-, and alkaline pH-induced conformational transitions, we constructed a phase diagram of the anion- and pH-dependent conformational transition. The phase diagram was similar in shape to that of acid-denatured apomyoglobin [Goto, Y., & Fink, A.L. (1990) J. Mol. Biol. 214, 803-805] or that of the amphiphilic Lys, Leu model polypeptide [Goto, Y., & Aimoto, S. (1991) J. Mol. Biol. 218, 387-396], suggesting a common mechanism of the conformational transition. The anion-, pH-, and peptide concentration-dependent conformational transition of melittin was explained on the basis of an equation in which the conformational transition is linked to proton and anion binding to the titratable groups.

[1]  K. Dill,et al.  Protein stability: electrostatics and compact denatured states. , 1991, Proceedings of the National Academy of Sciences of the United States of America.

[2]  Y. Goto,et al.  Anion and pH-dependent conformational transition of an amphiphilic polypeptide. , 1991, Journal of molecular biology.

[3]  N R Kallenbach,et al.  Side chain contributions to the stability of alpha-helical structure in peptides. , 1990, Science.

[4]  F E Cohen,et al.  Studies of synthetic helical peptides using circular dichroism and nuclear magnetic resonance. , 1990, Journal of molecular biology.

[5]  A. Fink,et al.  Phase diagram for acidic conformational states of apomyoglobin. , 1990, Journal of molecular biology.

[6]  K. Dill.  Dominant forces in protein folding. , 1990, Biochemistry.

[7]  A. Fink,et al.  Mechanism of acid-induced folding of proteins. , 1990, Biochemistry.

[8]  Robert L. Baldwin,et al.  Relative helix-forming tendencies of nonpolar amino acids , 1990, Nature.

[9]  P. S. Kim,et al.  Intermediates in the folding reactions of small proteins. , 1990, Annual review of biochemistry.

[10]  A. Fink,et al.  Acid-induced folding of proteins. , 1990, Proceedings of the National Academy of Sciences of the United States of America.

[11]  N. Go,et al.  Structure of melittin bound to perdeuterated dodecylphosphocholine micelles as studied by two-dimensional NMR and distance geometry calculations , 1989 .

[12]  A. Fink,et al.  Conformational states of beta-lactamase: molten-globule states at acidic and alkaline pH with high salt. , 1989, Biochemistry.

[13]  K. Kuwajima,et al.  The molten globule state as a clue for understanding the folding and cooperativity of globular‐protein structure , 1989, Proteins.

[14]  R. L. Baldwin,et al.  Helix stabilization by Glu-...Lys+ salt bridges in short peptides of de novo design. , 1987, Proceedings of the National Academy of Sciences of the United States of America.

[15]  O. Ptitsyn.  Protein folding: Hypotheses and experiments , 1987 .

[16]  Robert L. Baldwin,et al.  Tests of the helix dipole model for stabilization of α-helices , 1987, Nature.

[17]  William F. DeGrado,et al.  Induction of peptide conformation at apolar water interfaces. 1. A study with model peptides of defined hydrophobic periodicity , 1985 .

[18]  K. D. Collins,et al.  The Hofmeister effect and the behaviour of water at interfaces , 1985, Quarterly Reviews of Biophysics.

[19]  J. B. Matthew.  Electrostatic effects in proteins. , 1985, Annual review of biophysics and biophysical chemistry.

[20]  A. Wada,et al.  ‘Molten‐globule state’: a compact form of globular proteins with mobile side‐chains , 1983, FEBS letters.

[21]  C. C. Condie,et al.  Conformational studies of aqueous melittin: thermodynamic parameters of the monomer-tetramer self-association reaction. , 1983, Biochemistry.

[22]  S. Quay,et al.  Conformational studies of aqueous melittin: determination of ionization constants of lysine-21 and lysine-23 by reactivity toward 2,4,6-trinitrobenzenesulfonate. , 1983, Biochemistry.

[23]  D Eisenberg,et al.  The structure of melittin. II. Interpretation of the structure. , 1982, The Journal of biological chemistry.

[24]  E. Granados,et al.  Conformation and aggregation of melittin: dependence on pH and concentration. , 1982, Biochemistry.

[25]  D. Eisenberg,et al.  The structure of melittin. I. Structure determination and partial refinement. , 1981, The Journal of biological chemistry.

[26]  K. Wüthrich,et al.  High-resolution 1H-NMR studies of self-aggregation of melittin in aqueous solution. , 1980, Biochimica et biophysica acta.

[27]  K. Wüthrich,et al.  High-resolution 1H-NMR studies of monomeric melittin in aqueous solution. , 1980, Biochimica et biophysica acta.

[28]  J. Fritz,et al.  Anion chromatography with low-conductivity eluents , 1979 .

[29]  D. Eisenberg,et al.  Interactions of melittin, a preprotein model, with detergents. , 1979, Biochemistry.

[30]  J. Dufourcq,et al.  Conformational change and self association of monomeric melittin , 1979, FEBS letters.

[31]  E Habermann,et al.  Bee and wasp venoms. , 1972, Science.

[32]  R. Marcus,et al.  Studies on Ion-exchange Resins. XIII. Selectivity Coefficients of Quaternary Base Anion-exchange Resins Toward Univalent Anions , 1955 .