Protein Structural Changes Accompanying Formation of Enzymatic Transition States: Tryptophan Environment in Ground-State and Transition-State Analogue Complexes of Adenosine Deaminase

Linda C. Kurz, Derek LaZard, Carl Frieden

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

The accessibility of protein tryptophan fluorescence to the quenching agent acrylamide has been studied in adenosine deaminase and in binary complexes of the enzyme with ground-state or transition-state analogues. Although the enzyme contains three tryptophan residues, Stern-Volmer plots are linear with all the fluorescence quenchable at high acrylamide concentrations. Tryptophan fluorescence is less easily quenched in the binary complexes than in the free enzyme, indicating a decrease in the accessibility of these residues. The greatest decrease in accessibility is found for the transition-state analogue complexes. Although the affinities of the transition-state analogues studied span a range of 106, the Stern-Volmer constants of the complexes are the same within experimental error. Thus, as measured by this technique, changes in enzyme conformation accompanying formation of these complexes are similar for all transition-state analogues. Resonance energy transfer from tryptophan as donor to ligand as acceptor successfully explains the differing abilities of ligands to quench the enzyme's intrinsic fluorescence upon formation of complexes in the absence of acrylamide. On the basis of Forster distance calculations, it is likely that the residues partially quenched upon formation of transition-state analogue complexes are distant from the active site.

Original languageEnglish
Pages (from-to)1342-1346
Number of pages5
JournalBiochemistry
Volume24
Issue number6
DOIs
StatePublished - Mar 1 1985

Fingerprint

Dive into the research topics of 'Protein Structural Changes Accompanying Formation of Enzymatic Transition States: Tryptophan Environment in Ground-State and Transition-State Analogue Complexes of Adenosine Deaminase'. Together they form a unique fingerprint.

Cite this