J. Biol. Chem., Vol. 261, Issue 25, 11645-11649, Sep, 1986
Properties of cyclic AMP-independent catabolite gene activator proteins of Escherichia coli
B Blazy and A Ullmann
The protein products of two crp alleles encoding mutationally altered
catabolite gene activator proteins CAP and CAPc, which are functionally
active in vivo in the absence of cAMP, were purified by an immunoaffinity
purification procedure. These proteins bind cAMP with the same affinity as
does the wild-type catabolite gene activator protein. From their
susceptibility to the proteolytic enzyme subtilisin, we conclude that the
two mutationally altered proteins adopt structural features adequate for
biological activity and similar to the conformation that cAMP elicits or
stabilizes in wild-type catabolite gene activator protein. We note,
however, that their conformation is not unique and can be modulated by
cAMP. The two altered proteins, CAP and CAPc, bind to the lactose promoter,
giving rise to specific DNA-protein complexes in the absence of cAMP and
promote initiation of specific lac messenger RNA synthesis.