RNA helicase activity of Escherichia coli SecA protein.

SecA protein of Escherichia coli (E. coli), an ATPase essential for the translocation of precursor proteins, was found to have an additional activity of RNA helicase. This RNA unwinding activity of SecA was tested with two kinds of RNA duplex with different predicted stability. Each of these duplexes is consisted of two strands of unequal length with single-stranded ends. The RNA helicase activity of SecA required ATP and divalent cations. Confirmation of this activity came from the inhibition of unwinding of the RNA duplex when SecA was preincubated with its own polyclonal antibody. The biological significance of the RNA helicase activity of E. coli SecA protein is discussed.