Research Interests: Gene Expression; Protein Phosphorylation Cascades
Every biological process is regulated by several different control mechanisms. Our research focuses on how the individual mechanisms work and how they are coordinated with each other. We are studying the regulation of the glyoxylate bypass in the bacterium Escherichia coli. We chose this organism because it can be manipulated with a variety of powerful genetic techniques. Specific research projects make extensive use of molecular biology, genetics, protein chemistry, and enzymology.
In Escherichia coli, expression of the enzymes of the glyoxylate bypass is controlled by a complex network of transcription factors. Once induced, this pathway is regulated by a bifunctional protein kinase/phosphatase which phosphorylates a key metabolic enzyme. Projects in this system concern the control of gene expression and the structure and function of the kinase/phosphatase.
Unnikrishnan I, Miller S, Meinke M, LaPorte DC. (2003).Multiple positive and negative elements involved in the regulation of expression of GSY1 in Saccharomyces cerevisiae. J. Biol. Chem. 278:26450-7. (Medline citation)
Singh SK. Miller SP. Dean A. Banaszak LJ. LaPorte DC. "Bacillus subtilis isocitrate dehydrogenase - A substrate analogue for Escherichia coli isocitrate dehydrogenase kinase/phosphatase". J. Biol. Chem. 277, 7567 (2002). (Medline citation).
Sunnarborg SW. Miller SP. Unnikrishnan I. LaPorte DC. Expression of the yeast glycogen phosphorylase gene is regulated by stress-response elements and by the HOG MAP kinase pathway. Yeast. 18(16):1505-1514 (2001). (Medline citation).
Singh, S., Matsuno, K., LaPorte, D.C. and Banaszak, L. "Crystal Structure of B. subtilis Isocitrate Dehydrogenase at 1.55: Insights into the Nature of Substrate Specificity Exhibited by E. coli Isocitrate Dehydrogenase Kinase/Phosphatase". J. Biol. Chem. 276, 26163 (2001). (Medline citation).
Oudot C. Cortay JC. Blanchet C. Laporte DC. Di Pietro A. Cozzone AJ. Jault JM. "The "catalytic" triad of isocitrate dehydrogenase kinase/phosphatase from E-coli and its relationship with that found in eukaryotic protein kinases." Biochemistry 40, 3047 (2001). (Medline citation).
Miller, S.P., Chen, R., Karschnia, E.J., Romfo, C., Dean, A. and LaPorte, D.C. (2000) Locations of the Regulatory Sites for Isocitrate Dehydrogenase Kinase/Phosphatase. J. Biol Chem. 275(2):833-9. (Medline citation).
Miller, S.P., Anand, G.R., Karschnia, E.J., Bell, G.I., LaPorte, D.C. and Lange, A.J. (1999) Characterization of glucokinase mutations associated with maturity-onset diabetes of the young type 2 (MODY-2): Different glucokinase defects lead to a common phenotype. Diabetes. 48: 1645. (Medline citation).
Finer-Moore, J., Tsutakawa, S.E., Cherbavaz, D.R., LaPorte, D.C., Koshland, D.E. Jr, Stroud, R.M. (1997) Access to phosphorylation in isocitrate dehydrogenase may occur by domain shifting. Biochemistry 36(45):13890-6. (Medline citation).
Miller, S.P., Karschnia, E.J., Ikeda, T.P., LaPorte, D.C. (1996) Isocitrate dehydrogenase kinase/phosphatase. Kinetic characteristics of the wild-type and two mutant proteins. J. Biol. Chem. 271(32):19124-8. (Medline citation).