Abstract:
:We performed hole-burning Stark effect experiments on cytochrome c in which the iron of the herne was either removed or replaced by Zn. According to the experiments, the free-base compound has an effective inversion center, even in the protein. The Zn compound, on the other hand, shows quite peculiar features: in the low-frequency range of the inhomogeneous band, it definitely has a dipole moment, as indicated by a splitting of the hole in the external field. However, in the maximum of the inhomogeneous band, a severe charge redistribution occurs, as the experiments show. In addition to the Stark experiments, we performed calculations of the electrostatic fields at the pyrrole rings and at the metal site of the heme group. We interpret our findings with a model based on structural hierarchies: the protein can exist in a few subconformations, which can be distinguished through the structure of the heme pocket. The different pocket structures support different structures of the chromophore, which, in turn, can be distinguished through their behavior in an external field. These distinct structures, in turn, correspond to a rather broad distribution of protein structures, which leave, however, the pocket structure largely unchanged. These structures show up in inhomogeneous broadening.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Köhler M,Gafert J,Friedrich J,Vanderkooi JM,Laberge Mdoi
10.1016/S0006-3495(96)79237-8subject
Has Abstractpub_date
1996-07-01 00:00:00pages
77-85issue
1eissn
0006-3495issn
1542-0086pii
S0006-3495(96)79237-8journal_volume
71pub_type
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