Craig Helstowski
Description of Research:
X-ray crystallography is arguably the most popular tool used to calculate protein structure. However, a major limitation of the technique is that hydrogen atoms can only be seen at ultra high resolutions (< 1.0 Å). Less than 1% of all protein structures deposited into the Protein Data Bank (http://www.rcsb.org) achieve this type of resolution. Even in those structures that achieve ultra high resolution, not all of the protons can be viewed due to the high thermal motions that many of them exhibit, especially protons on water molecules or catalytic residues. However, neutron diffraction can distinguish hydrogen locations at resolutions down to 2.5 Å therefore increasing the feasibility of determining enzymatic catalytic mechanisms or water structures around proteins. Neutron difraction is being applied to gain further insight into the role that water plays in the inherent stability of ubiquitin as well as the mechanism of the water-mediated binding between ubiquitin and an ubiquitin specific protease (USP). Ubiquitin is known as an intracellular tag to mark proteins for either degradation or transport in eukaryotes. However, ubiquitin can be cleaved off its substrate by proteases before ubiquitin can deliver its substrate to its proper destination. One particular family of ubiquitin-cleaving enzymes is USP’s, several of which are implicated in several types of diseases. The first aim is to use neutron diffraction to discern the hydrogen-bonded water structure around ubiquitin. The next aim is to then use a combination of neutron diffraction with molecular dynamics to elucidate the hydrogen-bond network and dynamics of the sandwiched water molecules at the ubiquitin-USP interface and how these water molecules are able to stabilize a “wet” protein complex, a more rare type of protein-protein interaction.
Contact Information
Craig Helstowski
Prospective PhD Candidate, Class of 2007
Email: chelstow@utk.edu
Mentor
Dr. Dean Myles
Degree
BS: Biological Sciences, University of Connecticut