Protein Phosphorylation and Intermolecular Electron Transfer: A Joint Experimental and Computational Study of a Hormone Biosynthesis Pathway
- 15 March 2007
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 129 (14), 4206-4216
- https://doi.org/10.1021/ja064803j
Abstract
Protein phosphorylation is a common regulator of enzyme activity. Chemical modification of a protein surface, including phosphorylation, could alter the function of biological electron-transfer reactions. However, the sensitivity of intermolecular electron-transfer kinetics to post-translational protein modifications has not been widely investigated. We have therefore combined experimental and computational studies to assess the potential role of phosphorylation in electron-transfer reactions. We investigated the steroid hydroxylating system from bovine adrenal glands, which consists of adrenodoxin (Adx), adrenodoxin reductase (AdR), and a cytochrome P450, CYP11A1. We focused on the phosphorylation of Adx at Thr-71, since this residue is located in the acidic interaction domain of Adx, and a recent study has demonstrated that this residue is phosphorylated by casein kinase 2 (CK2) in vitro.1 Optical biosensor experiments indicate that the presence of this phosphorylation slightly increases the binding affinity of oxidized Adx with CYP11A1ox but not AdRox. This tendency was confirmed by KA values extracted from Adx concentration-dependent stopped-flow experiments that characterize the interaction between AdRred and Adxox or between Adxred and CYP11A1ox. In addition, acceleration of the electron-transfer kinetics measured with stopped-flow is seen only for the phosphorylated Adx−CYP11A1 reaction. Biphasic reaction kinetics are observed only when Adx is phosphorylated at Thr-71, and the Brownian dynamics (BD) simulations suggest that this phosphorylation may enhance the formation of a secondary Adx−CYP11A1 binding complex that provides an additional electron-transfer pathway with enhanced coupling.Keywords
This publication has 76 references indexed in Scilit:
- Coupling Coherence Distinguishes Structure Sensitivity in Protein Electron TransferScience, 2007
- Protein-protein association: investigation of factors influencing association rates by Brownian dynamics simulationsJournal of Molecular Biology, 2001
- Computer simulation of protein-protein association kinetics: acetylcholinesterase-fasciculinJournal of Molecular Biology, 1999
- Visualizing and quantifying molecular goodness-of-fit: small-probe contact dots with explicit hydrogen atomsJournal of Molecular Biology, 1999
- All-Atom Empirical Potential for Molecular Modeling and Dynamics Studies of ProteinsThe Journal of Physical Chemistry B, 1998
- VMD: Visual molecular dynamicsJournal of Molecular Graphics, 1996
- Electrostatics and diffusion of molecules in solution: simulations with the University of Houston Brownian Dynamics programComputer Physics Communications, 1995
- Selective chemical modification of cytochrome P-450SCC lysine residues. Identification of lysines involved in the interaction with adrenodoxinBiochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1989
- Rapid spectral scan and stopped-flow studies of carbon monoxide binding to bovine adrenocortical cytochrome P-450sccBiochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1987
- Steroidogenic electron transport in adrenal cortex mitochondriaMolecular and Cellular Biochemistry, 1982