The Transient Complex of Cytochrome c and Cytochrome c Peroxidase: Insights into the Encounter Complex from Multifrequency EPR and NMR Spectroscopy.

ABSTRACT: We present a novel approach to study transient protein-protein complexes with standard, 9?GHz, and high-field, 95?GHz, electron paramagnetic resonance (EPR) and paramagnetic NMR at ambient temperatures and in solution. We apply it to the complex of yeast mitochondrial iso-1-cytochrome c (Cc) with cytochrome c peroxidase (CcP) with the spin label [1-oxyl-2,2,5,5-tetramethyl-?3-pyrroline-3-methyl)-methanethiosulfonate] attached at position 81 of Cc (SL-Cc). A dissociation constant KD of 20±4×10-6 ?M (EPR and NMR) and an equal amount of stereo-specific and encounter complex (NMR) are found. The EPR spectrum of the fully bound complex reveals that the encounter complex has a significant population (60?%) that shares important features, such as the Cc-interaction surface, with the stereo-specific complex.

SUBMITTER: van Son M 

PROVIDER: S-EPMC7317791 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature