Michael K. Reddy
Biochemistry
Associate Professor
PhD, State University of New York at Stony Brook
(414) 229-5355
e-mail: mkr@uwm.edu
Selected Publications
Using both a prokaryotic and a eukaryotic virus as model systems, our research focuses upon fundamental cellular processes, such as DNA replication, which elicit a spectrum of protein-nucleic acid interactions. Interacting networks of properly functioning macromolecular complexes form the essential web responsible for the overall metabolism of biological organisms. Our goal is to obtain a precise understanding of the molecular basis of specificity that underlies the functions of these interacting components in vivo.
The Bacteriophage T4 SystemOne of the protein subassemblies required for DNA replication is termed the "Clamp Loader Complex" (CLC). During the process of DNA replication, the precise role of the CLC is to chaperone another oligomeric protein complex, termed the "Sliding Clamp", onto double stranded DNA. The Sliding Clamp, which has a three-dimensional structure best described as a "protein donut", subsequently interacts with the DNA polymerase and tethers it to the DNA template. The CLC possesses an intrinsic low-level ATPase activity that is stimulated 20-fold upon its interaction with either DNA or the Sliding Clamp. In the presence of both of these cofactors, the overall ATPase rate of the gp44/62 complex is increased an additional 100-fold! The molecular mechanism responsible for these observed catalytic increases remain unknown. Our laboratory is actively working towards deciphering this pathway by means of employing various crosslinking methodologies, including both chemical as well as molecular biological approaches, kinetic analysis of product release, and the development of novel protein chromatography strategies.
The Vaccinia Virus SystemVaccinia virus (VV) is the most-studied member of the Poxviridae. Poxviruses are distinguished among all other known DNA viruses by the fact that their life cycle occurs exclusively within the cytoplasm of the infected host cell. Poxviruses encode the vast majority of their own enzymatic components required for the transcription and replication of their genome. Due to its functional homology to its eukaryotic counterparts, the study of vaccinia virus has a long "track-record" of shedding light on parallel systems in human cells. At late times during the VV life cycle, an extremely complex series of virion assembly and maturation steps occurs, referred to as virus morphogenesis. The morphogenesis of VV begins with the appearance in the cytoplasm of "virus factories". These factories are the sites of viral transcription and DNA replication. Nearby these regions, crecent-shaped cisternal membranes emanate. From these crescents the spherical immature viruses (IVs) are made. IVs are the precursors of the first infectious form of the virus: the intracellular mature virus (IMV). The transition from IV to IMV is an extremely complex event in which membrane assembly of the viral envelope, proteolytic processing of structural proteins, and packaging of the genome into the viral core are all necessarily coordinated. The molecular details of these events are largely unknown and we hope to help unravel this process by a focused study on an essential protein called VP11. Previous work has established that VP11's yet-to-be-determined function lies at the heart of the IV to IMV transition. VP11 is a phosphoserine protein. Among VP11's possible roles is condesation of the viral DNA genome as part of a nucleoprotein complex with another viral protein called VP8. Using a combination of genetic, virological, ultrastructural, and biochemical techniques, our laboratory is currently addressing the following questions:
