Dynamical properties of cold shock protein A from Mycobacterium tuberculosis.

Bacterial cold shock proteins (Csps) are over-expressed as response to cold stress. They have a role in transcriptional and translational events due to their ability to bind single stranded (ss) nucleic acids. Csps so far characterized show similar structures with a closed five stranded antiparallel β-barrel. Here we report a structural and functional study of cold shock protein A from Mycobacterium tuberculosis, MTB-CspA. Structural investigations by CD and NMR reveal that MTB-CspA is less ordered than expected and is the least thermal stable cold shock protein so far characterized. However, electrophoretic mobility shift assays show that MTB-CspA is functionally active, as it is able to bind oligonucleotides. The dynamic behavior of MTB-CspA, compared to its homolog from Bacillus subtilis, was investigated by molecular dynamics simulations at room and high temperatures. Analysis of trajectories point to specific regions on β1 and β4 strands, likely responsible for the higher structural fragility of MTB-CspA. Also, they show that the nucleic-acid binding region of MTB-CspA is the least prone to unfolding, a finding which explains the ability of MTB-CspA to exert its function.