People
Robert E. Dempski
Assistant Professor
Office: Life Sciences and Bioengineering Center, 3005
Phone: +1-508-831-4193
Fax: +1-508-831-4116
rdempski@wpi.edu
Related Information
Educational Background
- B.S., Bucknell University, 1997
- Ph.D., Massachusetts Institute of Technology, 2003
Research & Teaching Interests
Biochemical and biophysical approaches to study the mechanism of membrane proteins in situ and in vitro.
Research
Our research focus is to combine biochemical and biophysical techniques to investigate a variety of membrane proteins. Previously, we have monitored the conformational dynamics and structural alignment of the Na,K-ATPase utilizing voltage clamp fluorometry.
The Na,K-ATPase is a plasma membrane protein which maintains a low internal Na+ concentration and a high internal K+ concentration against the prevailing ion gradients by utilizing the energy provided by ATP hydrolysis. Although much work has been to understand the molecular mechanism of the alpha subunit, little is known about the participation of the beta subunit in conformational changes of the enzyme. In order to elucidate the role of the beta subunit during ion transport, extracellular amino acids proximal to the transmembrane region of the sheep beta(1) subunit have been replaced for cysteines. This enabled sulfhydryl-specific labeling with the environmentally-sensitive fluorescent dye tetramethylrhodamine-6- maleimide (TMRM) upon expression in Xenopus oocytes. These experiments identified three reporter positions on the beta subunit that responded with fluorescence changes to alterations in ionic conditions and/or membrane potential and which demonstrate real-time detection of conformational rearrangements of the Na/K-ATPase beta subunit. In the course of these experiments, we have also been able to elucidate distance constraints and the relative movement of each subunit of the ion pump as a function of ion transport.
Our current research is focused on developing new techniques to further investigate the mechanism of additional membrane proteins either in situ or in vitro.