Thermal unfolding of tetrameric melittin: comparison with the molten globule state of cytochrome c.


Whereas melittin at micromolar concentrations is unfolded under conditions of low salt at neutral pH, it transforms to a tetrameric alpha-helical structure under several conditions, such as high peptide concentration, high anion concentration, or alkaline pH. The anion- and pH-dependent stabilization of the tetrameric structure is similar to that of the molten globule state of several acid-denatured proteins, suggesting that tetrameric melittin might be a state similar to the molten globule state. To test this possibility, we studied the thermal unfolding of tetrameric melittin using far-UV CD and differential scanning calorimetry. The latter technique revealed a broad but distinct heat absorption peak. The heat absorption curves were consistent with the unfolding transition observed by CD and were explainable by a 2-state transition mechanism between the tetrameric alpha-helical state and the monomeric unfolded state. From the peptide or salt-concentration dependence of unfolding, the heat capacity change upon unfolding was estimated to be 5 kJ (mol of tetramer)-1 K-1 at 30 degrees C and decreased with increasing temperature. The observed change in heat capacity was much smaller than that predicted from the crystallographic structure (9.2 kJ (mol of tetramer)-1 K-1), suggesting that the hydrophobic residues of tetrameric melittin in solution are exposed in comparison with the crystallographic structure. However, the results also indicate that the structure is more ordered than that of a typical molten globule state. We consider that the conformation is intermediate between the molten globule state and the native state of globular proteins. Study holds ProTherm entries: 10808, 10809 Extra Details: circular dichroism; differential scanning calorimetry; melittin;,molten globule state; thermal unfolding

Submission Details

ID: ToZR3hVq3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:40 p.m.

Version: 1

Publication Details
Hagihara Y;Oobatake M;Goto Y,Protein Sci. (1994) Thermal unfolding of tetrameric melittin: comparison with the molten globule state of cytochrome c. PMID:7833804
Additional Information

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Melittin P01502 MEL_APIDO