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Detecting equilibrium cytochrome c folding intermediates by electrospray ionisation mass spectrometry: Two partially folded forms populate the molten‐globule state
Author(s) -
Grandori Rita
Publication year - 2002
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.45102
Subject(s) - molten globule , chemistry , electrospray ionization , mass spectrometry , folding (dsp implementation) , crystallography , protein folding , conformational isomerism , chromatography , circular dichroism , organic chemistry , molecule , biochemistry , electrical engineering , engineering
Nanoelectrospray ionization mass spectrometry (nano‐ESI‐MS) is applied to the characterization of ferric cytochrome c (cyt c ) conformational states under different solvent conditions. The methanol‐induced molten‐globule state in the pH range 2.6–3.0 is found to be populated by two distinct, partially folded conformers I A and I B . The more compact intermediate I B resembles that induced by glycerol in acid‐unfolded cyt c . The less compact one, I A , also can be induced by destabilization of the native structure by trifluoroethanol. I A and I B can be detected, in the absence of additives, around the midpoint of the acid‐induced unfolding transition, providing direct evidence for involvement of equilibrium folding intermediates in cyt c conformational transitions at low pH. This study shows that mass spectrometry can contribute to the characterization of molten‐globule states of proteins by detection of distinct, although poorly populated, conformations involved in a dynamic equilibrium.