Enables 5S rRNA primary transcript binding activity. Predicted to be involved in positive regulation of translation and tRNA processing. Located in euchromatin and nucleus. Is expressed in several structures, including embryonic/larval midgut primordium; gut section; head epidermis primordium; muscle cell; and somatic trunk mesoderm derivative. Orthologous to human SSB (small RNA binding exonuclease protection factor La).