Linked Life Data

12488095

Source:http://linkedlifedata.com/resource/pubmed/id/12488095

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2002-12-18
pubmed:abstractText
We have previously proposed a model for the fold of the N-terminal domain of the small, regulatory subunit (SSU) of acetohydroxyacid synthase isozyme III. The fold is an alpha-beta sandwich with betaalphabetabetaalphabeta topology, structurally homologous to the C-terminal regulatory domain of 3-phosphoglycerate dehydrogenase. We suggested that the N-terminal domains of a pair of SSUs interact in the holoenzyme to form two binding sites for the feedback inhibitor valine in the interface between them. The model was supported by mutational analysis and other evidence. We have now examined the role of the C-terminal portion of the SSU by construction of truncated polypeptides (lacking 35, 48, 80, 95, or 112 amino acid residues from the C terminus) and examining the properties of holoenzymes reconstituted using these constructs. The Delta35, Delta48, and Delta80 constructs all lead to essentially complete activation of the catalytic subunits. The Delta80 construct, corresponding to the putative N-terminal domain, has the highest level of affinity for the catalytic subunits and leads to a reconstituted enzyme with k(cat)/K(M) about twice that of the wild-type enzyme. On the other hand, none of these constructs binds valine or leads to a valine-sensitive enzyme on reconstitution. The enzyme reconstituted with the Delta80 construct does not bind valine, either. The N-terminal portion (about 80 amino acid residues) of the SSU is thus necessary and sufficient for recognition and activation of the catalytic subunits, but the C-terminal half of the SSU is required for valine binding and response. We suggest that the C-terminal region of the SSU contributes to monomer-monomer interactions, and provide additional experimental evidence for this suggestion.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0022-2836
pubmed:author
pubmed:issnType
Print
pubmed:day
10
pubmed:volume
325
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
275-84
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
The N-terminal domain of the regulatory subunit is sufficient for complete activation of acetohydroxyacid synthase III from Escherichia coli.
pubmed:affiliation
Department of Life Science, Ben-Gurion University POB 653, 84105, Beer-Sheva, Israel
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't