Deregulation of acetohydroxy-acid synthase: Loss of allosteric inhibition conferred by mutations in the catalytic subunit
Jazyk angličtina Země Spojené státy americké Médium print-electronic
Typ dokumentu časopisecké články, práce podpořená grantem
- MeSH
- acetolaktátsynthasa chemie genetika metabolismus MeSH
- aktivace enzymů MeSH
- alosterická regulace genetika MeSH
- bakteriální proteiny chemie genetika metabolismus MeSH
- bodová mutace MeSH
- katalytická doména genetika MeSH
- konformace proteinů MeSH
- missense mutace MeSH
- molekulární modely MeSH
- rekombinantní fúzní proteiny chemie metabolismus MeSH
- sekvenční homologie aminokyselin MeSH
- Streptomyces enzymologie genetika MeSH
- substituce aminokyselin MeSH
- valin metabolismus MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- acetolaktátsynthasa MeSH
- bakteriální proteiny MeSH
- rekombinantní fúzní proteiny MeSH
- valin MeSH
Acetohydroxy-acid synthases (AHAS) of two mutant strains Streptomyces cinnamonensis ACB-NLR-2 and BVR-18 were chosen for this study for their apparent activation by valine, which regularly acts as an allosteric inhibitor. Sequencing the ilvB genes coding for the AHAS catalytic subunit revealed two distant changes in the mutants, DeltaQ217 and E139A, respectively. Homology modeling was used to propose the structural changes caused by those mutations. In the mutant strain ACB-NLR-2 (resistant to 2-amino-3-chlorobutyrate and norleucine), deletion of Q217 affected a helix in ss-domain, distant from the active center. As no mutation was found in the regulatory subunit of this strain, DeltaQ217 in IlvB was supposed to be responsible for the observed valine activation, probably via changed properties on the proposed regulatory-catalytic subunit interface. In mutant strain BVR-18 (resistant to 2-oxobutyrate), substitution E139A occurred in a conservative loop near the active center. In vitro AHAS activity assay with the enzyme reconstituted from the wild-type regulatory and BVR-18 catalytic subunits proved that the substitution in the catalytic subunit led to the apparent activation of AHAS by valine. We suggest that the conservative loop participated in a conformational change transfer to the active center during the allosteric regulation.
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