An acetylatable lysine controls CRP function in E. coli.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Transcriptional regulation ensures precise protein expression timing and quantity.
• The cAMP receptor protein (CRP) is a key transcription factor in Escherichia coli.
• Regulation of CRP activity itself remains an area of investigation.

Purpose of the Study:

• To investigate the regulatory mechanisms of CRP activity.
• To elucidate the role of specific residues on CRP function.
• To understand how CRP activity is modulated under different metabolic conditions.

Main Methods:

• Site-directed mutagenesis to alter CRP lysine residues.
• In vitro assays to measure CRP binding and transcriptional activity.
• Analysis of CRP protein levels in vivo.
• Metabolic flux analysis under varying growth conditions.

Main Results:

• A surface lysine residue (K100) on CRP exhibits dual functions.
• K100 promotes CRP activity at Class II promoters and maintains CRP steady-state levels.
• Acetylation of K100 by acetyl phosphate neutralizes its positive charge, reducing Class II promoter activity.
• Acetylation of K100 leads to elevated CRP steady-state levels, indirectly boosting Class I promoter activity.

Conclusions:

• CRP K100 acetylation serves as a regulatory mechanism to tune gene expression.
• This acetylation modulates CRP activity and protein levels in response to metabolic cues.
• The proposed mechanism is relevant during conditions favoring acetate fermentation, such as growth on glucose.