Enzymes are typically studied in ensembles. Enzyme mechanism has traditionally been elucidated from biochemical and structural experiments that involve thousands or millions of molecules. Enzymes, however, are complex molecular machines that, when subjected to individual scrutiny, reveal features that cannot be ascertained from ensemble approaches. Single-molecule visualization and manipulation techniques are at the technological forefront of biological enquiry; these techniques can probe distances on the sub-nanometer (10-9 M) scale and forces on the piconewton (10-12 N) scale with millisecond temporal resolution. Dr. Neuman employs these techniques—including optical and magnetic tweezers and fluorescence imaging, in combination with conventional molecular biology approaches—to answer fundamental questions concerning enzyme function and regulation. His research program is underpinned by single-molecule instrumentation that his laboratory designs and builds to elucidate enzyme mechanisms at the molecular level.
Approximately two meters of DNA is compacted into a cell’s nucleus, which leads to topological complications during replication, transcription, and segregation of chromosomes. Topoisomerases are essential enzymes that regulate DNA topology and are important chemotherapeutic and antibiotic drug targets; Dr. Neuman focuses on elucidating the molecular mechanisms of topoisomerase activity and inhibition by chemotherapeutic agents.
Topoisomerases interact with many other enzymes that regulate DNA. Dr. Neuman is extending the use of single-molecule techniques to dissect multi-enzyme complex formation and activity. For this work, he focuses on the combination of RecQ helicase and topoisomerase III, which is a conserved interaction in organisms ranging from E. coli through humans and plays important roles in genome stability and chromosome segregation.
Moving beyond the cell nucleus, and beyond the cell, Dr. Neuman studies the interaction between the structural protein collagen and the matrix metalloproteinase enzymes (collagenase) that remodel collagen. By measuring the motion of individual collagenase enzymes as they move along and degrade individual native collagen fibrils he can probe aspects of fibrillar collagen and the cleavage process. This enzymatic degradation reaction is important in a host of human pathological and physiological process including the rupture of atherosclerotic plaques and cancer metastasis.
Keir Neuman, Ph.D., applies physics to transform the field of biology at the National Institutes of Health (NIH) Intramural Research Program (IRP). Dr. Neuman is a Principal Investigator in the Laboratory of Single Molecule Biophysics at the National Heart Lung and Blood Institute (NHLBI).