Journal of Microbiology

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Gly184 of the Escherichia coli cAMP receptor protein provides optimal context for both DNA binding and RNA polymerase interaction: Matt N. Hicks , Sanjiva Gunasekara , Jose Serate , Jin Park , Pegah Mosharaf , Yue Zhou , Jin-Won Lee , Hwan Youn; J. Microbiol. 2017;55(10):816-822. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7266-x

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The Escherichia coli cAMP receptor protein (CRP) utilizes the helix-turn-helix motif for DNA binding. The CRP’s recognition helix, termed F-helix, includes a stretch of six amino acids (Arg180, Glu181, Thr182, Val183, Gly184, and Arg185) for direct DNA contacts. Arg180, Glu181 and Arg185 are known as important residues for DNA binding and specificity, but little has been studied for the other residues. Here we show that Gly184 is another F-helix residue critical for the transcriptional activation function of CRP. First, glycine was repeatedly selected at CRP position 184 for its unique ability to provide wild type-level transcriptional activation activity. To dissect the glycine requirement, wild type CRP and mutants G184A, G184F, G184S, and G184Y were purified and their in vitro DNA-binding activity was measured. G184A and G184F displayed reduced DNA binding, which may explain their low transcriptional activation activity. However, G184S and G184Y displayed apparently normal DNA affinity. Therefore, an additional factor is needed to account for the diminished transcriptional activation function in G184S and G184Y, and the best explanation is perturbations in their interaction with RNA polymerase. The fact that glycine is the smallest amino acid could not fully warrant its suitability, as shown in this study. We hypothesize that Gly184 fulfills the dual functions of DNA binding and RNA polymerase interaction by conferring conformational flexibility to the F-helix.

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cAMP-independent DNA binding of the CRP family protein DdrI from Deinococcus radiodurans
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mBio.2024;[Epub] CrossRef
Unexpected Requirement of Small Amino Acids at Position 183 for DNA Binding in the Escherichia coli cAMP Receptor Protein
Marcus Carranza, Amanda Rea, Daisy Pacheco, Christian Montiel, Jin Park, Hwan Youn
Journal of Microbiology.2024; 62(10): 871. CrossRef
cAMP Activation of the cAMP Receptor Protein, a Model Bacterial Transcription Factor
Hwan Youn, Marcus Carranza
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