The Transient Complex of Cytochrome c and Cytochrome c Peroxidase: Insights into the Encounter Complex from Multifrequency EPR and NMR Spectroscopy |
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Authors: | Martin van Son Jesika T Schilder Antonella Di Savino Anneloes Blok Prof Marcellus Ubbink Dr Martina Huber |
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Institution: | 1. Leiden Institute of Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden (The, Netherlands;2. Leiden Institute of Chemistry, Leiden University, Gorlaeus Laboratories, Einsteinweg 55, 2333 CC Leiden (The, Netherlands |
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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-Δ3-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. |
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Keywords: | cytochrome high-field EPR paramagnetic NMR principal component analysis transient protein complex |
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