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Structural heterogeneity of the various forms of apomyoglobin; Implications for protein folding
Author(s) -
Gilmanshin Rudolf,
Dyer R. Brian,
Callender Robert H.
Publication year - 1997
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 - 10.1002/pro.5560061008
Subject(s) - chemistry , myoglobin , denaturation (fissile materials) , protein folding , molten globule , folding (dsp implementation) , crystallography , nucleation , tryptophan , native state , kinetics , protein structure , fluorescence , biophysics , chemical physics , circular dichroism , amino acid , biochemistry , organic chemistry , physics , quantum mechanics , biology , electrical engineering , nuclear chemistry , engineering
Temperature‐induced denaturation transitions of different structural forms of apomyoglobin were studied monitoring intrinsic tryptophan fluorescence. It was found that the tryptophans are effectively screened from solvent both in native and acid forms throughout most of the temperature range tested. Thus, the tryptophans' surroundings do not show a considerable change in structure where major protein conformational transitions have been found in apomyoglobin using other techniques. At high temperatures and under strong destabilizing conditions, the tryptophans' fluorescence parameters show sigmoidal thermal denaturation. These results, combined with previous studies, show that the structure of this protein is heterogeneous, including native‐like (tightly packed) and molten globule‐like substructures that exhibit conformation (denaturation) transitions under different conditions of pH and temperature (and denaturants). The results suggest that the folding of this protein proceeds via two “nucleation” events whereby native‐like contacts are formed. One of these events, which involves AGH “core” formation, appears to occur very early in the folding process, even before significant hydrophobic collapse in the rest of the protein molecule. From the current studies and other results, a rather detailed picture of the folding of myoglobin is presented, on the level of specific structures and their thermo‐dynamical properties as well as formation kinetics.