• Contact:
• Email:
  

  michael.e.harris
  @case.edu

• Office Location:
  

  Wood W106

• Office Phone:
  

  216-368-4779

• Fax:
  

  216-368-2010

• Laboratory Location:
  

  W110

• Laboratory Phone:
  

  216-268-0381

• Faculty List
• Michael E. Harris Overview

Research:

Molecular recognition and catalysis by the ribonuclease P: A ribonucleoprotein enzyme.
Analysis of phosphoryl transfer mechanisms using kinetic isotope effects.

Global structure of the RNase P enzyme–substrate complex.
(a) Consensus secondary structure of bacterial RNase P RNA. Individual helices are given the designation P, for paired, and numbered from the 50 end of the RNA. HelixP4 is shown as gray bars connected by a line. Elements of non-Watson–Crick structure between helices are given the designation J, for joining, and numbered for the helices they connect. Structural elements referred to in the text are indicated. Blue and green lines indicate the path of the phosphodiester backbone; universally conserved nucleotide positions are designated by capital letters. The catalytic domain, or C-domain, is shown in green, whereas the specificity domain, or S-domain, is shown in blue. The stacked acceptor and T-stems of pre-tRNA that are recognized by RNase P are shown in red. Specific substrate elements recognized by RNase P are indicated by capital letters. The pre-tRNA cleavage site is indicated by an arrow. Known interactions between the ribozyme and substrate are shown by lines connecting the interacting positions in RNase P RNA and pre-tRNA. The interaction between the RNase P protein and the substrate 50 leader sequence is indicated by a gray oval. (b)Global three-dimensional structure derived from manual computer modeling of the E. coli RNase P RNA–pre-tRNA complex. Colors of the C-domain, the S-domain and pre-tRNA are the same as in (a). The probable location of the RNase P protein is indicated by a dashed black circle and the proposed path of the 50 leader sequence is indicated by a dashed red line.
From Harris and Christian (2003). Curr. Op. Struct. Biol. 13, 325-333.

Positions of metal ion interactions within the NMR structure of the universally conserved P4 helix in RNase P RNA. The locations of individual functional groups involved in divalent metal ion interactions, as determined by biochemical analysis of site-specific functional group modifications, are shown in the context of the three-dimensional structure of an isolated P4 helix. Phosphate oxygen (red and yellow) and purine N7 (blue) functional groups involved in metal contacts are shown as spheres. Yellow spheres represent phosphorothioate-sensitive positions that are rescued by Mn2þ, indicating sites of direct metal ion coordination. A conserved bulged uridine residue important for optimal metal ion binding is in red.
From Harris and Christian (2003). Curr. Op. Struct. Biol. 13, 325-333.

Effects of deprotonation and direct coordination by Mg2+ on the observed solvent nucleophile isotope effect ( 18knuc ) provide information about reaction mechanism. Coordination of water by Mg2+ exhibits an inverse (0.99) isotope effect (18Kcoord). Magnesium will also perturb the equilibrium isotope effect on deprotonation of water to form hydroxide (18KOH), resulting in a similar inverse shift in the observed effect. It is also possible that metal ion interactions can alter the intrinsic kinetic isotope effect for bond formation (18kbond); however, metal ion coordination does not appear to alter the transition state for monoester hydrolysis.
From Cassano, Anderson, and Harris (2004). Biochemistry. 43(32):10547-59.