| Abstract
| - Several studies have shown that anions induce collapse of acid-denatured cytochrome c intothe compact A state having the properties of the molten globule and that the anion charge is the maindeterminant for the A state stabilization. The results here reported show that the anion size plays a rolein determining the overall structure of the A state. In particular, small anions induce formation of an Astate in which the native Met80−Fe(III) axial bond is recovered and the nativelike redox properties restored.On the other hand, the A state stabilized by large anions shows a histidine (His26 or His33) as the sixthligand of the heme-iron, a very weak interaction between Trp59 and the heme propionate, and lacksnativelike redox properties. The two anion-stabilized states show similar stability, indicating that (i) thehydrophobic core (which is equally stabilized by all the anions investigated, independently of their size)is the region that mainly contributes to the macromolecule stabilization, and (ii) the flexible loops areresponsible for the spectroscopic (and, thus, structural) and redox differences observed.
|
