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Functional roles of the two cyclic AMP‐dependent forms of cyclic AMP receptor protein from Escherichia coli
Author(s) -
Mukhopadhyay Jayanta,
Sur Runa,
Parrack Pradeep
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00719-x
Subject(s) - receptor , cyclic gmp , chemistry , escherichia coli , biochemistry , protein kinase a , camp receptor protein , cyclic peptide , biophysics , biology , kinase , enzyme , gene , promoter , gene expression , peptide
The cyclic AMP receptor protein activates transcription in Escherichia coli , only when complexed with cyclic AMP. The cyclic AMP receptor protein‐cyclic AMP complex formed at low concentrations of cyclic AMP has a different conformation from either cyclic AMP receptor protein alone or its complex with cyclic AMP formed at high cyclic AMP concentrations. Various biophysical data suggest that the latter complex resembles free cyclic AMP receptor protein. We have examined the conformational and biological properties of cyclic AMP receptor protein as a function of cyclic AMP concentrations, using the gal operon of E. coli . A biphasic behavior is observed. It is shown that only the complex formed at lower concentrations of cyclic AMP is the transcriptionally active form. This difference between the complexes at different levels of cyclic AMP arises from a decreased ability of the cyclic AMP receptor protein‐cyclic AMP complex at high cyclic AMP concentrations to bind to DNA at specific sites.