Avidin as a probe of the conformational changes induced in pyruvate carboxylase by acetyl‐CoA and pyruvate

FEBS Letters

Wallace, John C.¹  Mayer, Frank²  Attwood, Paul V.¹ 

[1] Department of Biochemistry, University of Adelaide, Adelaide, South Australia 5001, Australia;Institut für Mikrobiologie der Georg-August-Universität zu Göttingen, Grisebachstrasse 8,D-3400 Göttingen, FRG

关键词: Pyruvate carboxylase;    Allosteric activation;    Conformational change;    Acetyl-CoA;    Pyruvate;    Avidin;   

DOI  :  10.1016/0014-5793(86)80740-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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.

【 授权许可】

Unknown