The most abundant DEAD-box RNA helicase. An ATP-dependent RNA helicase with RNA-dependent ATPase activity. May work in conjunction with the cold shock proteins to ensure proper initiation of transcription at low and optimal temperatures. In vitro, unwinds dsRNA in both 5'- and 3'- directions. Plays a role in ribosomal 50S subunit assembly. Its deletion leads to changes in mRNA levels for over 200 transcripts. ATP + H2O = ADP + H(+) + phosphate RNA helicase activity is inhibited by EDTA. Homodimer or oligomer. May interact with RNA helicases CshB and DbpA (DeaD). Probably a component of the RNA degradosome complex composed of rny, rnjA, rnjB, pnp, pfkA and eno, and possibly also rnpA (although rnjA and rnjB's presence is unclear). Interacts with ribosomal proteins L1 and L3 (rplA and rplC) and the protein component of RNase RnpA. Interacts with the RNA polymerase core (PubMed:21710567). Shows transcription-dependent localization at subcellular sites surrounding the nucleoid (PubMed:16352840). Associated with free 50S ribosomal subunit, 70S ribosome and polysomes (PubMed:16861794). Cell membrane association shown in (PubMed:20572937). Induced by cold shock (PubMed:12399512). Constitutively expressed at 37 and 16 degrees Celsius in rich and minimal medium and in exponential, transition and stationary phase (at protein level) (PubMed:20572937, PubMed:23175651). Protein level not increased at 16 degrees Celsius (at protein level) (PubMed:20572937). The C-terminal half of the protein (residues 225-494) is required for interaction with most RNA degradosome partners, whereas dimerization or oligomerization only requires the extreme C-terminus (residues 413-494). Addition of the latter domain to CshB confers on it the ability to interact with Rny. Slow vegetative growth at 37 degrees Celsius, impaired growth at 22 degrees Celsius (PubMed:16861794) and 16 degrees Celsius (PubMed:23175651). Another report shows no growth difference at 15 degrees Celsius (PubMed:16352840). The presence of CshA or CshB is essential for viability; in a cshA disruption mutant further depletion of cshB stops growth after 1 cell duplication (PubMed:16352840). Others show a quadruple disruption of all RNA helicases (cshA, cshB, deaD, yfmL) was not lethal at 37 degrees Celsius, although both 50S and 70S ribosomes are decreased, growth stops at 16 degrees (PubMed:23175651). At 20 degrees Celsius cells are elongated and wrinkled, with smaller cell diameter and thickened walls, and decreased amounts of 70S and 50S ribosomes; levels of over 200 transcripts are altered (PubMed:23175651). Belongs to the DEAD box helicase family. CshA subfamily. Extended N-terminus.