Premium
Comprehensive characterization of ligand‐induced plasticity changes in a dimeric enzyme
Author(s) -
Baettig Oliver M.,
Shi Kun,
Yachnin Brahm J.,
Burk David L.,
Berghuis Albert M.
Publication year - 2016
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13788
Subject(s) - allosteric regulation , cooperativity , chemistry , protein data bank (rcsb pdb) , crystallography , enzyme , substrate (aquarium) , circular dichroism , transferase , ligand (biochemistry) , stereochemistry , biochemistry , biology , receptor , ecology
An enzyme's inherent structural plasticity is frequently associated with substrate binding, yet detailed structural characterization of flexible proteins remains challenging. This study employs complementary biophysical methods to characterize the partially unfolded structure of substrate‐free AAC (6′)‐Ii, an N ‐acetyltransferase of the GCN5‐related N ‐acetyltransferase ( GNAT ) superfamily implicated in conferring broad‐spectrum aminoglycoside resistance on Enterococcus faecium . The X‐ray crystal structure of AAC (6′)‐Ii is analyzed to identify relative motions of the structural elements that constitute the dimeric enzyme. Comparison with the previously elucidated crystal structure of AAC (6′)‐Ii with acetyl coenzyme A (AcCoA) reveals conformational changes that occur upon substrate binding. Our understanding of the enzyme's structural plasticity is further refined with small‐angle X‐ray scattering and circular dichroism analyses, which together reveal how flexible structural elements impact dimerization and substrate binding. These results clarify the extent of unfolding that AAC (6′)‐Ii undergoes in the absence of AcCoA and provide a structural connection to previously observed allosteric cooperativity of this enzyme. Database Structural data are available in the PDB database under the accession number 5E96 .