Dr. Crampton was an instructor at Harvard Medical School in 2005-2006, and has held appointments at Boston College and Tufts University.
Postdoctoral Fellow, Harvard Medical School, 2001-2005
Ph.D. Botany, Arizona State University, 2000
B.A. Biochemistry, Ithaca College, 1994
Current Research and Teaching
Research in our laboratory is organized around bacterophage, viruses that infect and kill bacteria. Bacteriophage (or phage) represent the largest depository of genomic DNA in the biosphere with an estimate of 1031 or more individual bacteriophase on the earth. Phage also have an integral role in molecular biology -- for example, restriction enzymes evolved as a bacterial defense against phage infection and enzymes such as ligase and polynucleotide kinase come from phage-encoded genes. In the Crampton Laboratory, we have two bacteriophage related research areas: mitochondrial DNA replication and discovery of bacteriophage specific for disease causing bacteria.
Mitochondrial DNA Replication
Mitochondria are the energy producing organelle in the cell, and the only organelle in animal cells besides the nucleus that contains its own chromosome. Given the bacterial ancestry of mitochondria, one might expect that the essential elements of genome maintenance would resemble those of bacteria. However, this is not the case for the DNA polymerase or the replicative helicase, which appear to have a shared ancestry with proteins of T-odd bacteriophages.
Our laboratory is working to characterize the role of the helicase in the mitochondrial replisome using both mammalian and Arabidopsis thaliana systems.& Helicases are molecular machines that use the energy from nucleotide hydrolysis to unwind double-stranded DNA. The replicative helicase found in both bacteriophage and mitochondria is a bifunctional protein containing both a helicase domain and a primase domain. Primases synthesize short ribooligonucleotide primers to facilitate the binding of DNA polymerase. We are keenly interested in the role of the primase region in mitochondrial DNA replication -- something that has yet to be understood.
As the number of bacterial genomes that have been sequenced increases, more and more bacteria are found to contain stable prophages, phage genomes that have been integrated into the bacterial chromosome. Sometime before the symbiotic event that lead to cellular mitochondria, prophage replication genes replaced those replication genes encoded by the bacterial genome. Our lab also is investigating the possible steps of such a mechanistic swap as occurred in the evolution of mitochondria.
Our other project relies on two widely held beliefs about bacteriophage. First, phage population densities exceed bacterial densities by a ratio of 10-to-1 or more. Hence, bacteriophage represent a huge repository of genomic wealth consisting of gene products with unknown but potentially useful functions. Second, bacteriophages have evolved unique proteins that arrest critical cellular processes to commit bacterial host metabolism to phage reproduction.
Presently, we are searching for bacteriophage specific for the bacterium Strepococcus mutans, the leading cause of dental tooth decay worldwide.
Bacteriophage can be found in all reservoirs populated by bacterial hosts, such as soil or the intestines of animals. Our source of bacteriophage is the traps underneath the sinks of Clark University's dormitoris -- where large numbers of students brush their teeth and deposit S. mutans from their mouths to the sink drains. Specifically, we are actively looking for lytic or virulent phage that may contain gene products which inhibit the growth of S. mutans.
Courses that I am involved in include Biochemistry, Bioanalytical Cemistry, Protein Chemistry, and Forensics. I am also an active member of the American Society for Biochemistry and Molecular Biology and the Council for Undergraduate Research.
Besides my obvious interests in biochemistry and molecular biology, I am an avid reader of science fiction literature. Since my days as an undergraduate, I have been intrigued by the idea of science fiction as a bridge betweeen the "two cultures" of the sciences and humanities. I have quite a large collection of science fiction novels in my office which can be borrowed by students.
Stop by my office, chat about Sci-Fi, learn about science, and maybe even get involved in research.
“Oligomeric States of the Bacteriophage T7 Helicase-Primase,” Donald J. Crampton, Melanie Ohi, Udi Qimron, Thomas Walz, and Charles C. Richardson (2006). Journal of Molecular Biology 360, 667-677.
“DNA-induced Switch from Independent to Sequential dTTP Hydrolysis in the Bacteriophage T7 Helicase,” Donald J. Crampton, Sourav Mukherjee, and Charles C. Richardson (2006). Molecular Cell 21, 165-174.
“The Arginine Finger of Bacteriophage T7 Gene 4 Helicase: Role in Energy Coupling,” Donald J. Crampton, Shenyuan Guo, Donald E. Johnson, and Charles C. Richardson (2003). Proceedings of the National Academy of Sciences (USA) 101, 4373-4378.
“Single-molecule kinetics of lambda exonuclease reveal base dependence and dynamic disorder,” Antoine van Oijen, Paul C. Blainey, Donald J. Crampton, Charles C. Richardson, Tom Ellenberger, and X. Sunney Xie (2003). Science 301, 1235-1238.