Protein-protein and protein-nucleic acid interactions are the molecular machinery of life. Understanding the underlying molecular structures, how they drive these interactions, and the cellular processes that they regulate, is the goal of the Melcher lab at the Van Andel Institute in Grand Rapids, Michigan. Prof. Karsten Melcher leads the Laboratory of Structural Biology and Biochemistry in VAI’s Center for Cancer and Cell Biology, oriented to identifying druggable pathways and receptors for diseases such as diabetes, cancer and neurological disorders. The lab utilizes X-ray crystallography and cryo-EM for detailed structural studies, but when these are not possible – light scattering helps fill the gaps.
Dr. Melcher’s career has spanned various fields and locations. After receiving undergraduate and graduate degrees from Germany, at the Universities of Bochum, Tűbingen, and Frankfurt, and completing postdoctoral training in the U.S. at UT Southwestern Medical Center. From there he went on to establish research groups in Frankfurt, Germany and then Ulster in the United Kingdom. In 2007, he joined VAI, which is an independent biomedical research and science education organization committed to improving the health, and enhancing the lives, of current and future generations. He now holds the rank of professor in VAI’s Structural Biology Program.
Though he started his career as a classically trained yeast geneticist, later on Karsten became a protein biochemist and a structural biologist. Due in part to this background, his current structural work focuses on cellular signaling, from signal reception to gene regulation. The Melcher group is deeply interested in understanding the molecular architecture of multiprotein complexes, which is where light scattering plays an important role. The ability of SEC-MALS to calculate the absolute molecular weight of a protein complex fractionated by size exclusion chromatography (SEC) is an important first step in deducing the stoichiometry of its subunits. This capability, implemented with their miniDAWN® MALS instrument and Optilab® dRI detector, is especially insightful for complexes that are difficult to analyze using high-resolution structural techniques such as x-ray crystallography or cryo-EM. They have also used a DynaPro® NanoStar® to carry out dynamic light scattering measurements, demonstrating that a specific transcriptional repression motif can induce co-repressor oligomerization as a novel mechanism of gene repression and epigenetic regulation.
MALS and DLS are natural complements of other techniques utilized in structural biology. Light scattering is useful for quality control of proteins after purification and before SAXS or SANS studies, identification of optimal crystallization buffers prior to x-ray scattering, quantification of protein-protein interactions, or—as described above—for analysis of complexes in solution. To explore more, see www.wyatt.com/Proteins.
We use our SEC-MALS system, incorporating a miniDAWN and Optilab to calculate the absolute molecular weight of a protein complex in solution. This is an important first step in deducing the stoichiometry of its subunits towards understanding the molecules' structure and function