SrmB, a DEAD-box helicase involved in Escherichia coli ribosome assembly, is specifically targeted to 23S rRNA in vivo.

DEAD-box proteins play specific roles in remodeling RNA or ribonucleoprotein complexes. Yet, in vitro, they generally behave as nonspecific RNA-dependent ATPases, raising the question of what determines their specificity in vivo. SrmB, one of the five Escherichia coli DEAD-box proteins, participates in the assembly of the large ribosomal subunit.