Reinhart Reithmeier

Research Synopsis

My laboratory is interested in the structure and function of membrane proteins, in particular the chloride/bicarbonate anion exchanger (AE1, Band 3). The Band 3 glycoprotein of the erythrocyte membrane is responsible for the exchange of chloride and bicarbonate across the plasma membrane, a process necessary for respiration. A truncated form of the protein (kAE1) is expressed in the kidney where it plays an essential role in bicarbonate re-absorption.

A major aim of our research is to determine, at the molecular level, the mechanism of action of the human chloride/bicarbonate anion exchanger (AE1) and a truncated version kAE1, expressed in the kidney. We are also interested in determining the effect of mutations in the AE1 (SLC4A1) gene, linked to various hematological and kidney diseases, on the biosynthesis and function of the protein. A wide variety of structural, cellular and molecular biological techniques are employed in our research.

We have grown small 3-dimensional crystals and 2-dimensional arrays of the human Band 3 protein and we are determining its structure by X-ray diffraction and electron microscopy. A Band 3 homologue identified in yeast is being characterized with the aim of determining its structure. The structure of the cytosolic domain of normal and mutant kAE1, expressed in E. coli , is also being studied using various biophysical techniques. We are also working on the expression and crystallization of bacterial anion transporters (SLC26A/SulP) related to AE1.

We are studying the effects of mutations in Band 3 on biosynthesis and folding of this membrane protein using cell-free systems and transfected cells. We are particularly interested in the role of chaperones in mediating the proper folding and trafficking of this membrane protein. The interaction of Band 3 with glycophorin A, carbonic anhydrase, cytoskeletal and other cytosolic proteins is also a current interest. One goal is to identify the AE1 interactome, the full complement of interacting proteins using proteomics and membrane yeast 2-hybrid methods.

The interactions between various transmembrane segments in Band 3 and with the lipid bilayer is being simulated by computer modeling. Basic principles of membrane protein structure are being established by analyses of the amino acid sequences in membrane protein data banks.