TY - JOUR
T1 - Three amino acids in Escherichia coli CspE surface-exposed aromatic patch are critical for nucleic acid melting activity leading to transcription antitermination and cold acclimation of cells
AU - Phadtare, Sangita
AU - Tyagi, Sanjay
AU - Inouye, Masayori
AU - Severinov, Konstantin
PY - 2002/11/29
Y1 - 2002/11/29
N2 - Cold-shock proteins of the CspA family of Escherichia coli help the cells to acclimate to low temperature conditions through an unknown mechanism. In vitro, these proteins bind to single-stranded nucleic acids and destabilize nucleic acid secondary structures. An unusual surface-exposed patch of 6 evolutionarily conserved aromatic amino acids is thought to be involved in RNA binding by the cold-shock proteins. Here we investigated the functional role of the aromatic patch in E. coli CspE by substituting individual aromatic residues with positively charged Arg residues. These substitutions do not affect the RNA binding activity of the CspE mutants. We show that substitutions of three centrally located aromatic patch amino acid residues, Phe17, Phe30, and His32, abolish the ability of the mutant CspE to acclimatize cells to cold, antiterminate transcription and melt nucleic acids but have no effect on RNA binding. On the other hand, peripherally located Trp10, Phe19, and Phe33 can be substituted with Arg without loss of any of the in vivo and in vitro CspE functions tested. The results thus indicate that these aromatic patch residues have clearly distinct functional roles and further extend the correlation between the essential function of CspA homologues in cold acclimation and their ability to antiterminate transcription.
AB - Cold-shock proteins of the CspA family of Escherichia coli help the cells to acclimate to low temperature conditions through an unknown mechanism. In vitro, these proteins bind to single-stranded nucleic acids and destabilize nucleic acid secondary structures. An unusual surface-exposed patch of 6 evolutionarily conserved aromatic amino acids is thought to be involved in RNA binding by the cold-shock proteins. Here we investigated the functional role of the aromatic patch in E. coli CspE by substituting individual aromatic residues with positively charged Arg residues. These substitutions do not affect the RNA binding activity of the CspE mutants. We show that substitutions of three centrally located aromatic patch amino acid residues, Phe17, Phe30, and His32, abolish the ability of the mutant CspE to acclimatize cells to cold, antiterminate transcription and melt nucleic acids but have no effect on RNA binding. On the other hand, peripherally located Trp10, Phe19, and Phe33 can be substituted with Arg without loss of any of the in vivo and in vitro CspE functions tested. The results thus indicate that these aromatic patch residues have clearly distinct functional roles and further extend the correlation between the essential function of CspA homologues in cold acclimation and their ability to antiterminate transcription.
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U2 - 10.1074/jbc.M208118200
DO - 10.1074/jbc.M208118200
M3 - Article
C2 - 12324471
AN - SCOPUS:2242461342
SN - 0021-9258
VL - 277
SP - 46706
EP - 46711
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 48
ER -