Research Interests

The main focus is the study of enzymes that hydrolyze disaccharides. Most of the studies carried out concern the action of Beta-galactosidase from E. coli. Beta-Galactosidase hydrolyzes disaccharides having _ linkages to D-galactose. In particular, the enzyme hydrolyzes lactose, which is the sugar found in milk. The enzyme is being studied as a model of enzymes that hydrolyze disaccharides in general. The main approach taken is an analysis of the residues of the enzyme that are important for substrate binding and catalysis by site-specific mutagenesis. Residues on the enzyme of potential significance are being systematically substituted by other residues and the effect is being studied kinetically and physically. The residues that have thus far been found to be important for activity are Glu-461, Tyr-503, Glu-537, Gly-794, Glu-416, His-418, His-357, His-391, His-540, Trp-999 and Trp-568

Selected publications

• J.C. Kappelhoff, S.Y. Liu, M.L. Dugdale, D.L. Dymianiw, L. R. Linton, R.E. Huber Practical Considerations When Using Temperature to Obtain Rate Constants and Activation Thermodynamics of Enzymes with Two Catalytic Steps: Native and N460T-ß-Galactosidase (E. coli) as Examples. Protein J 28:96–103 (2009).
  
• D.H. Juers, B. Rob, M.L. Dugdale, N. Rahimzadeh, C. Giang, M. Lee, B.W. Matthews, and R.E. Huber Direct and indirect roles of His-418 in metal binding and in the activity of ß-galactosidase (E. coli). Protein Science 18:1281-1292 (2009).
  
• Sutendra, G., Wong, S., Fraser, M.E. and Huber, R.E. ß-Galactosidase (Escherichia coli) has a second catalytically important Mg2+ site. Biochem. Biophys. Res. Comm. 352 566 – 570 (2007).
• Seidle, H.F., Allison, S.J., George, E. and Huber, R.E. Trp-49 of the family 3 ß-glucosidase from Aspergillus niger is important for its transglucosidic activity: Creation of novel ß-glucosidases with low transglucosidic efficiencies. Arch. Biochem. Biophys. 455, 110 – 118 (2006).
  
• Moriguchi, T., Takako, N., Hamada, M., Maeda, A., Fujioka, Y., Kurohha, R., Huber, R.E., Hasegawa, S.L., Rao, A., Yamamoto, M., Takahashi, S., Lim, K-C. and Engel, J.D. Gata3 participates in a
• complex transcriptional feedback network to regulate synpathoadrenal differentiation. Development 133, 3871 – 3881 (2006).
• H.F. Seidle, K. McKenzie, I. Marten, O. Shoseyov and R.E. Huber. Trp-262 is a key residue for hydrolytic and transglucosidic reactivity of Aspergillus niger family 3 ß-glucosidases: substitution results in very high transglucosidic activity. Arch. Biochem. Biophys. 444, 66 –75 (2005).
• H.F. Seidle and R.E. Huber. Transglucosidic reactions of the Aspergillus niger family 3 ß-glucosidase: qualitative and quatitative analysis and evidence that the transglucosidic rate is independent of pH. Arch. Biochem. Biophys. 436: 254-264 ((2005).
• H.F. Seidle, I. Martin, O. Shoseyov and R.E. Huber. Physical and kinetic properties of the family 3 ß-glucosidase from Aspergillus niger which is important for cellulose breakdown. Protein Journal 23: 11-23 (2004).
• J. Xu, M.A.A. McRae, S. Harron, B. Rob, and R.E. Huber. A study of interactions between Asp201, Na+ or K+, and galactosyl C6 hydroxyl and their effects on binding and reactivity of ß-galactosidase. Biochem. Cell Biol. 82: 275-284 (2004).
• R.E. Huber, S. Hakda, C. Cheng, C.G. Cupples, and R.A. Edwards Trp-999 of Beta-galactosidase (Escherichia coli) is a key residue for binding, catalysis and synthesis of allolactose, the natural Lac operon inducer. Biochemistry 42 (2003), 1796 - 1803.
• B. Rob and R.E. Huber Beta-D-Galactopyranosyl azide: Its one-step synthesis using E461G-Beta-galactosidase (Escherichia coli) and a demonstration of its potential as a reagent for molecular biology. Applied Biochemistry and Bacteriology 104 (2003), 97 - 104.
• D.H. Juers, S. Hakda, B.W. Matthews, and R.E. Huber Structural basis for the altered activity of Gly794 variants of Esherichia coli Beta-galactosidase. Biochemistry 42 (2003) 13505- 13511.
• N.J. Roth, R.M. Penner and R.E. Huber Beta-Galactosidases (Escherichia coli) with double substitutions show that Tyr-503 acts independently of Glu-461 but cooperatively with Glu-537. J. Protein Chemistry 22 (2003), 663 - 668.
• Huber, R.E., I.H. Hlede, N.J. Roth, K.C. McKenzie, and K.K. Ghumman. 2001. His-391 of Beta-galactosidase (Esherichia coli) promotes catalysis by strong interactions with the transition state. Biochemistry and Cell Biology 79: 183-193.
• Richard, J.P., R.E. Huber and D.A. McCall. 2001. Effect of an E461G mutation of Beta-galactosidase (Esherichia coli) on pL rate profiles and solvent deuterium isotope effects. Bioorganic Chemistry 29:146-155.
• Huber, R.E. 2001. Beta -galactosidase. Encylopedia of Genetics (2001) 212-214.
• Juers, D.H., R.H. Jacobson, D. Wigley, X.-J. Zhang, R.E. Huber, D.E. Tronrud and B.W. Mathews (2000). High resolution refinement of Beta -galactosidase in a new crystal form reveals multiple metal-binding sites and provides a structural basis for a -complementation. Protein Science 9: 1685-1699.