Structure and function of proteins by x-ray diffraction analysis
The
three-dimensional structure of a protein plays a central role in
determining its function. One of the best tools for studying structure
is X-ray crystallography. My group uses this technique to investigate
the relationship between structure and function for large proteins and
macromolecular assemblies. There are several areas under investigation
in the laboratory many of which focus on proteins associated with the
cytoskeleton. A major goal is to understand the molecular basis for
movement with an emphasis on myosin-based molecular motors.
Myosin
Motility is one of the hallmarks of life. To accomplish this feat
nature has evolved a limited number of molecular motors that include
three superfamilies in eukaryotic cells, myosin, kinesin and dynein.
My group has devoted considerable effort to understanding myosin. This
is the major protein component of muscle, in which it plays both an
enzymatic and structural role. Interestingly, myosin has also been
found in all muscle cells where it plays a role in cytokinesis,
phagocytosis, endocytosis, cell division and axonal transport. Our
current efforts are directed towards: understanding the details of how
myosin functions as an ATPase, understanding novel aspects of
non-muscle myosin structure and function, and trapping myosin at
representative points around its contractile cycle. These studies
involve a combination of molecular biology, structural biology, and
enzymology.
Cobalamin Biosynthesis
A second interest is to understand how nature synthesizes complex organic molecules. My group, in collaboration with Dr. Jorge Escalante-Semerena
(Department of Bacteriology) has developed a long-term project to
understand the structural basis of cobalamin (vitamin B12)
biosynthesis. This is a challenging problem since total synthesis
requires upwards of 30 enzymes, however the lessons learned here can be
applied to many other biosynthetic pathways.
Ribbon representation of the Tn5 transposase/DNA dimer
viewed along a crystallographic two-fold axis of symmetry. One protein
subunit is colored yellow, the other is blue, and the two 20 bp DNA
molecules are purple. The three catalytic residues and the Mn2+
bound to the active site are represented as grey ball-and-stick
structures. This reveals that for each DNA molecule most of the
sequence specific protein-DNA interactions arise from one subunit,
whereas the other subunit is reponsible for cleavage. Such an
arrangement requires dimerization to occur prior to excision of the
transposase and explains many aspects of transposition