th  - 1988 - 51st ENC Conference

THU 8:30 "TETHERED" BIOLOGICAL SYSTEMS: RESULTS FROM NMR SPECTROSCOPY
Lynn W. Jelinski," Ronald W. Behling, David Live, + and Tetsuo Yamane, AT&T Bell Laboratories, Murray Hill, NJ 07974.
By "tethered" biological systems, we mean assemblies in which two or more molecules arc either covalently or transiently
joined together for the purpose of biological action. Tethered systems are a recurring theme in biophysics; examples include
enzyme - subswate complexes, DNA - protein interactions, receptor - ligand binding, and antigen - antibody recognition.
NMR spectroscopy is exceptionally well-suited to address key questions regarding both site - site recognition and chain
folding in tethere.d biological assemblies.
We will briefly describe three examples of tethered assemblies. In the first, polymer - peptide hybrids were constructed of
polystyrene onto which was grown oligoglycines with varying but monodisperse chain lengths. Using solid state deuterium
NMR spectroscopy, we showed that peptidc - peptide association occurred when the chain lengths were sufficient to form one
overlap of the polyglycine II triple helical repeat.
In another example, high resolution proton NMR was used to study the binding of small ligands to the acetylcholine receptor.
Once the strategy was in place for observation of binding by NMR, 2D-NOE experiments were performed to determine the
conformation of acetylcholine in its receptor-bound state. The results show that the conformation of the receptor in the
bound state is significantly different from that when free in solution, suggesting that structure-activity relationships based
solely on X-ray or solution conformations must be approached with caution.
We are presently attempting to answer the question of whether nucleation sites for protein folding are formed during protein
synthesis. To answer this question, we are preparing "fake" ribosomes (polyacrylamide) onto which the initial peptide
segments of the S-peptide of ribonuclease are attached. These "fake" ribosomes are designed to mimic the way in which a
protein would be synthesized in the cell. These tethered structures will be compared to the NMR spectra of the S-peptide,
whose solution state conformation is being determined.
Taken together, our results suggest that a combination of modem NMR techniques and cleverly chosen systems will have a
substantial impact on our understanding of the structure and function of complex hybrid biological systems.
+ Department of Chemistry, Emery University, Atlanta, GA 30322
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