Interdisciplinary PhD in Structural and Computational Biology and Quantitative Biosciences

Katherine Henzler-Wildman

Associate Professor, Department of Biochemistry Lab Website henzlerwildm@wisc.edu(608) 890-1094

471C HF DeLuca Biochemistry Laboratories
433 Babcock Drive
Madison, WI 53706-1544

Education

B.A., Cornell University
Ph.D., University of Michigan, Ann Arbor

Dynamics and function of integral membrane proteins, secondary active transport, ion channels

Dynamics and Function of Integral Membrane Proteins
Cartoon for membrane proteins are active molecules that move molecules or relay signals across membrane barriers. Many membrane proteins are active molecules that move molecules or relay signals across membrane barriers. To fully understand the function of these proteins, not only the structure, but the timescale, amplitude, and directionality of structural changes must be determined. We use NMR as our primary technique to monitor protein structure and dynamics, taking advantage of the extensive resources available through NMRFAM. By comparing our NMR data with biochemical and functional assays, we gain insight into the mechanisms of substrate transport, multidrug recognition, ion channel gating and ion selectivity.

Secondary Active Transport
Titration imageProtein conformational change is required for active transport, allowing alternating access to either side of the membrane in order to move a substrate against its electrochemical gradient. In the case of secondary transporters, the energy source for this process is the “downhill” flow of a second substrate, often protons. Our research investigates the protein dynamics central to the transport process and the critical coupling between substrates used to drive net transport.

We are currently studying the small multidrug resistance transporter, EmrE, one of the smallest known active transporters. EmrE functions as a homodimer, pumping polyaromatic cations out of E. coli and conferring resistance to drugs matching this chemical description. The cartoon presents a model of the conformational changes believed to occur during the EmrE transport cycle. Our research focuses on three broad questions: How does such EmrE recognize and actively transport such a diverse set of substrates? How is drug efflux coupled to proton import? What are the key structural and dynamic features required for active transport? How does the lipid environment affect EmrE structure, dynamics, and transport?

A second project examines the GLUT family of eukaryotic sugar transporters. The GLUTs have play an important role transporting glucose across the plasma membrane into mammalian cells. Our goals are to develop the NMR and biochemical tools needed to tackle large, challenging eukaryotic membrane proteins and gain insight into the mechanism of glucose transport in humans.

Ion Channels
Small bacterial ion channels serve as simplified model systems for dissecting the molecular mechanisms underlying fundamental channel properties, such as ion selectivity and channel gating. The NaK channel is a non-selective cation channel from Bacillus cereus that can be converted to a potassium-selective channel with two point mutations. The very high quality of NaK NMR spectra and availability of multiple high-resolution crystal structures make it an ideal system to study how ion selectivity arises from the atomic-resolution structure and dynamics of the channel.

Photo of Katie Henzler-Wildman

Areas of Expertise

  • Biophysical Chemistry
  • Membrane & Cellular Biophysics
  • Microbial Biophysics & Virology
  • Protein Folding Design & Function
  • Structural Biology