The main focus of our lab’s structure-function
work has been on the terminal enzymes of heme biosynthesis, protoporphyrinogen
oxidase (PPO) and ferrochelatase (FC). Through a variety of techniques
including protein expression and purification, site-directed mutagenesis,
spectroscopy, biochemical characterization, and X-ray
crystallography, we and our collaborators are investigating the mechanism
of action of these enzymes, and the consequences of mutations
in these proteins in the human genetic diseases known as porphyrias.
Our
lab has collaborations with several groups at the University of Georgia.
Following our initial identification of a [2Fe-2S] cluster in human
ferrochelatase, we have maintained an ongoing collaboration with
Michael Johnson’s group characterizing the [2Fe-2S]
clusters of several different classes of ferrochelatases. In collaboration
with
B.-C. Wang’s group we solved the first structure of human ferrochelatase
in 2001. This provided new information as to the membrane association of the
enzyme, key catalytic residues and location of the [2Fe-2S] cluster. Subsequently
with William Lanzilotta’s group we have been involved in determining
the structure of some variants including key catalytic residues and
surface residues. Most recently we have solved the structure of a ferrochelatase
variant with one of the substrates, protoporphyrin IX, bound. This new structure
has provided surprising information on the
enzyme mechanism, specifically demonstrating that the tight-binding competitive
inhibitor, N-alkylporphyrins, are not transition state analogs. The movie showing
the binding of porphyrin to ferrochelatase originates from this collaboration.
Current structure function studies in the Dailey lab are focusing on obtaining
crystals and solving the structure of ferrochelatase with both substrates
bound and with product bound. We also have ongoing structure-function
studies on bacterial and eukaryotic PPOs and a newly identified bacterial heme
synthesis protein that we have named HemQ.
