Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:3.4.21.1 (
chymotrypsin
)
10,938
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The Escherichia coli
AraC
protein represses and induces the araBAD operon in response to the absence or presence of l-arabinose. Constitutive mutations in the
AraC
gene no longer require the presence of l-arabinose to convert
AraC
from its repressing to its inducing state. Such mutations were isolated directly by virtue of their constitutivity or by their resistance to the nonmetabolizable arabinose analog, d-fucose. The majority of the constitutive mutations lie within the same residues of the N-terminal regulatory arm of
AraC
. Two, however, were found in the core of the dimerization domain. As predicted by the light switch mechanism of
AraC
, constitutive mutations increase the susceptibility of the N-terminal arms to digestion by trypsin or
chymotrypsin
, suggesting that these mutations weaken or disrupt the arm structure required for repression by
AraC
. Fluorescence, circular dichroism, and cysteine reactivity measurements show that the constitutive mutations in the core of the dimerization domain lead to a weakening of the support for the arms and reduce the stability of the minus-arabinose arm structure. These mutations also weaken the interaction between the two-helix bundle and the beta-barrel subdomains of the dimerization domain and reduce the structural stability of the beta-barrels.
...
PMID:Constitutive mutations in the Escherichia coli AraC protein. 1921 88
