Glycerol kinase (GK) from Escherichia coli is allosterically controlled by fructose 1,6-bisphosphate (FBP) and the glucose-specific phosphocarrier protein IIAGlc of the phosphotransferase system. These controls allow glucose to regulate glycerol utilization. Fluorescence spectroscopic and enzyme kinetic methods are applied to investigate these allosteric controls in this study. The linkage between FBP binding and GK tetramer assembly is solved by observation of homo-fluorescence energy transfer of the fluorophore Oregon Green (OG) attached specifically to an engineered surface cysteine in GK. FBP binds to tetramer GK with an affinity 4000-fold higher than to dimeric GK. A region named the coupling locus that plays essential roles in the allosteric signal transmission from the IIAGlc binding site to the active site was identified in GK. The relationship between the coupling locus sequence in Escherichia coli or Haemophilus influenzae GK variants and the local flexibility of the IIAGlc binding site is established by fluorescence anisotropy determinations of the OG attached to the engineered surface cysteine in each variant. The local flexibility of the IIAGlc binding site is influenced by the coupling locus sequence, and in turn affects the binding affinity for IIAGlc. Furthermore, the local dynamics of each residue in the IIAGlc binding site of GK is studied systematically by the fluorescence anisotropy measurements of OG individually attached to each position of the IIAGlc binding site. The fluorescence steady-state anisotropy measurement provides a valid estimation of the local flexibility and correlates well with the crystallographic B-factors. Steady-state kinetics of FBP inhibition shows that the data are best described by a model in which the partial inhibition and FBP binding stoichiometry are taken into account. Kinetic viscosity effects show that the product-release step is not the purely rate-limiting step in the GK-catalyzed reaction. Viscosity effects on FBP inhibition are also discussed.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/1537 |
| Date | 17 February 2005 |
| Creators | Yu, Peng |
| Contributors | Pettigrew, Donald W. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 2328712 bytes, electronic, application/pdf, born digital |
Page generated in 0.0018 seconds