Premium
Avidin as a probe of the conformational changes induced in pyruvate carboxylase by acetyl‐CoA and pyruvate
Author(s) -
Attwood Paul V.,
Mayer Frank,
Wallace John C.
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)80740-2
Subject(s) - pyruvate carboxylase , avidin , pyruvate dehydrogenase phosphatase , pyruvate decarboxylation , pyruvate dehydrogenase kinase , dihydrolipoyl transacetylase , biochemistry , chemistry , pkm2 , pyruvate dehydrogenase complex , acetyl coa , enzyme , allosteric regulation , pyruvate kinase , biotin , glycolysis
Sheep liver pyruvate carboxylase was mixed with avidin at a molar ratio of 1:1 in the presence of various combinations of the components of the assay systems required for either the acetyl‐CoA‐dependent or the acetyl‐CoA‐independent activity and negatively stained samples were examined by electron microscopy. Significant numbers of chain‐like polymers of enzyme‐avidin complexes were evident only when acetyl‐CoA or high levels of pyruvate were present in the media. Similar results were also obtained for chicken liver pyruvate carboxylase despite this enzyme's almost complete lack of acetyl‐CoA‐independent activity. Thus, although acetyl‐CoA and high concentrations of pyruvate may induce pyruvate carboxylase to adopt a ‘tight’ tetrahedron‐like conformation which can interact with avidin to form chains, this structural change alone does not result in an enzymic form that is maximally active. This suggests that the allosteric activation of pyruvate carboxylase by acetyl‐CoA is attributable, at least in part to more subtle conformational changes, especially in the case of the chicken enzyme.