Role of small subunit (IlvN polypeptide) of acetohydroxyacid synthase I from Escherichia coli K-12 in sensitivity of the enzyme to valine inhibition.
AUTOR(ES)
Eoyang, L
RESUMO
Most of the coding sequence for the IlvN polypeptide subunit of acetohydroxyacid synthase I was deleted from the ilvB+ ilvN+ plasmid pTCN12 by in vitro methods. Several ilvB+ delta ilvN derivatives of pTCN12 were identified among transformants of a strain otherwise lacking any acetohydroxyacid synthase. Deletion derivatives produced an enzymatically active IlvB polypeptide, as shown by the Ilv+ phenotype of transformed cells and by immunologic and enzymatic assays. However, whereas the growth of pTCN12 transformants was sensitive to valine inhibition, growth of the ilvB+ delta ilvN transformants was relatively resistant. Moreover, in vitro analyses confirmed that both acetolactate and acetohydroxybutyrate synthesis in extracts of the ilvB+ delta ilvN transformants was resistant to valine inhibition, in comparison with that in extracts of pTCN12 transformants or with that catalyzed by purified acetohydroxyacid synthase I. The IlvN polypeptide had a minimal effect, if any, on IlvB polypeptide accumulation as measured by immunoprecipitation, but its absence resulted in a greater than 10-fold reduction in enzyme specific activity.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=215211Documentos Relacionados
- Purification and subunit composition of acetohydroxyacid synthase I from Escherichia coli K-12.
- The ilvB locus of Escherichia coli K-12 is an operon encoding both subunits of acetohydroxyacid synthase I.
- Valine-Resistant Escherichia coli K-12 Strains with Mutations in the ilvB Operon
- Multivalent regulation of isoleucine-valine transaminase in an Escherichia coli K-12 ilvA deletion strain.
- Alkylation of acetohydroxyacid synthase I from Escherichia coli K-12 by 3-bromopyruvate: evidence for a single active site catalyzing acetolactate and acetohydroxybutyrate synthesis.
