Protein-protein interactions of the phenylpropanoid pathway in sorghum bicolor.

Abstract

Phenylalanine ammonia-lyase (PAL) is the first enzyme of the phenylpropanoid pathway followed by cinnamate 4-hydroxylase (C4H), a cytochrome P450 monooxygenase associated with the endoplasmic reticulum of plant cells. PAL and C4H are important for the plant cells due to their involvement in kickstarting the production of primary and secondary metabolites such as phenylpropanoids and lignin. C4H also interacts with cytochrome P450 reductase (CPR; Sorghum bicolor CPR in this study) to hydrolyze trans-cinnamic acid into p-coumaric acid. This study uses fluorescence correlation spectroscopy and single-protein fluorescence tracking of labeled proteins to directly measure the interactions of all three proteins in the absence and presence of their respective substrates. This study also explores specific protein-lipid interactions as a function of state (i.e. oxidation state, heterodimeric state, substrate occupancy, etc.)