Site-specific hydrolysis of horse heart cytochrome c and apocytochrome c promoted by palladium(II) complex

Horse heart cytochrome c and apocytochrome c (with the Fe-porphyrin removed ), which have completely different conformations, are selectively cleaved a t the same site in the presence of cis-[Pd(dtco-3-OH)(H2O)(2)](2+) (dtco-3- OH=dithiacycrooctan-3-ol). The cleaved fragments were separated by SDS-poly acrylamide gel electrophoresis and the cleavage yields were determined by a scanning densitometer. The site and size of cleavage were confirmed by pre cisely determining molecular masses of the proteins and of the cleaved frag ments using electrospray mass spectrometry. Different pH behavior in the cl eavage of cytochrome c and apocytochrome c is observed due to a requirement of a partially unfolded state II of the cytochrome c. Although the Pd(II) complex coordinates to different sulfur forms of Cys17 in the cytochrome c and the apocytochrome c (thioether in the former and thiolate anion in the latter), their cleavage yields at pH<2 are comparable. (C) 1999 Elsevier Sc ience Ltd. All rights reserved.