Potential Rotation Projects

Project #1: Probing the structural basis for cooperativity in a dimeric hemoglobin: Scapharca dimeric hemoglobin is an elegantly simple model system for exploring the structural basis for intersubunit communication. Our analysis to date has established a new paradigm for cooperativity in which tightly bound water molecules are used as sensors for ligand state.

In this project, the student will first mutate the gene for the native hemoglobin at a residue that is suspected of playing a role in the intersubunit communication. The mutated protein will then be expressed in E. coli and purified and subjected to functional analysis of oxygen binding. Using conditions already established for the native protein, the mutant hemoglobin will then be crystallized and subjected to preliminary x-ray analysis.

This project will provide the student with an introduction to two of the most powerful techniques for investigating the structure and function of proteins: site-directed mutagenesis and x-ray crystallography. Additionally, valuable experience in protein purification will be obtained.

Project #2: Structural analysis of the polymerization of sickle-cell hemoglobin Sickle cell disease results from the pathological polymerization of deoxygenated hemoglobin S (ß6E->V) within erythrocytes. This polymerization depends upon a complicated interplay of multiple interactions between tetramers. Our high resolution crystal structure of this molecule has elucidated details of some of the important interactions. Several projects are available for rotation students. These include crystallization of sickle-cell hemoglobin in the presence of an inhibitor to identify its binding site, site-directed mutagenesis of hemoglobin S and crystallization of mutants that show altered polymerization characteristics.