Cold-Shock Protein A (CspA)
CspA is the major cold-shock protein of the bacterial organism Escherichia coli. It is expressed during times of temperature decrease from 37 degrees Celcius to 10 degrees Celcius. A time lag of about 4 hours occurs when cell growth is temporarily stopped and the cold-shock proteins are induced. During the cold-shock response, CspA accounts for 10% or more of the total cellular protein.
CspA is a nucleic acid binding protein that binds to single stranded RNA of 74 base pairs or greater with very low sequence specificity. The binding of CspA to ssRNA inhibits any secondary structures from forming in the RNA because CspA functions to keep RNA unfolded. Thus at low temperatures, CspA acts as an RNA chaperone by keeping mRNAs free of secondary structure formation. This protein's biological function has an effect on both the translation of mRNA in the cell and transcription regulation at low temperatures.
CspA is 70 amino acid residues long and has a molecular weight of 7.4 kDa. The protein consists of 5 anti-parallel beta-sheets. The picture of CspA is colored by secondary structure.
This is CspA with eight surface aromatic side chains visible:
The eight aromatic side chains shown here that form the "aromatic ridge" of CspA are: Trp11, Phe12, Phe18, Phe20, Phe31, His33, Phe34, and Tyr42. This face of the protein forms the CspA-DNA complex suggesting that these surface side chains function in complex formation. This also suggests that CspA interacts with nucleic acids through hydrophobic interactions. The colors are as follows: Tryptophan=Purple, Phenylalanine=Green, Histidine=Silver, and Tyrosine=Gold.
An older model of MEF
Keywords for CspA: Transcription Regulation, DNA-Binding, Activator, and Multigene Family
View this protein's PDB entry as 1MEF
View this protein's entry in the SwissProt database as CSPA_ECOLI
K. Newkirk, W. Feng, W. Jiang, R. Tejero, S.D. Emerson, M. Inouye, G.T. Montelione
Solution NMR Structure of the Major Cold Shock Protein (CSPA) From Escherichia coli: Identification of a Binding Epitope for DNA.
Proc.Nat.Acad.Sci.USA 91:5114 (1994)
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