Two-dimensional nuclear magnetic resonance studies of thymosin-alpha(1) (a myosin light chain kinase activating peptide), and ribonuclease a in the presence of uridine vanadate.

Abstract

1. The structure of the peptide thymosin \alpha\sb1 has been investigated by circular dichroism and one- and two-dimensional nuclear magnetic resonance spectroscopy. Thymosin \alpha\sb1 is a highly acidic peptide composed of 28 amino acid residues. Through the use of circular dichroism and two-dimensional nuclear magnetic resonance techniques, the structure of thymosin \alpha\sb1 in 30% (v/v) deuterated 2,2,2-trifluoroethanol has been solved. Thymosin \alpha\sb1 contains an $\alpha$-helix extending from residue 16 to 26 and a turn between residues 5 and 8. Thymosin \alpha\sb1 has been shown to be a potent activator of skeletal muscle myosin light chain kinase, a well known calmodulin-dependent enzyme. Using the solution structures of thymosin \alpha\sb1 and the calmodulin binding domain of skeletal muscle myosin light chain kinase, computer modelling suggests that electrostatic interactions comprise the major interacting force between these two peptides. 2. The binding of the proposed transition state analog, uridine vanadate to ribonuclease A has been investigated by one- and two-dimensional nuclear magnetic resonance spectroscopy. Analysis of the homonuclear nuclear Overhauser end exchange spectroscopy spectrum of the uridine vanadate/ribonuclease A complex exhibits cross peaks between the H$\varepsilon$1 proton of histidine 12 of RNase A and both the C\sb6H and C\sb5H protons of uridine vanadate. No cross peaks were observed between the H$\varepsilon$1 proton of histidine 119 of ribonuclease A and the C\sb6H and C\sb5H protons of uridine vanadate. However, the distances calculated from the crystallographic structure show that the H$\varepsilon$1 proton of histidine 119 is closer to the C\sb6H and C\sb5H protons of uridine vanadate, than is the H$\varepsilon$1 proton of histidine 12. These results suggests that there is a significant difference in the position of the histidine 119 side chain in the crystallographic and solution structures of the uridine vanadate/ribonuclease A complex.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1994 .V43. Source: Dissertation Abstracts International, Volume: 56-11, Section: B, page: 6099. Adviser: Lana Lee. Thesis (Ph.D.)--University of Windsor (Canada), 1995