CLONING AND CHARACTERIZATION OF A BACILLUS-SUBTILIS GENE ENCODING A HOMOLOG OF THE 54-KILODALTON SUBUNIT OF MAMMALIAN SIGNAL RECOGNITION PARTICLE AND ESCHERICHIA-COLI FFH

By using a DNA fragment of Escherichia coli ffh as a probe, the Bacill us subtilis ffh gene was cloned. The complete nucleotide sequence of t he cloned DNA revealed that it contained three open reading frames (OR Fs). Their order in the region, given by the gene product, was suggest ed to be ORF1-Ffh-S16, according to their similarity to the gene produ cts of E. coli, although ORF1 exhibited no significant identity with a ny other known proteins. The orf1 and ffh genes are organized into an operon. Genetic mapping of the ffh locus showed that the B. subtilis f fh gene is located near the pyr locus on the chromosome. The gene prod uct of B. subtilis ffh shared 53.9 and 32.6% amino acid identity with E. coli Ffh and the canine 54-kDa subunit of signal recognition partic le, respectively. Although there was low amino acid identity with the 54-kDa subunit of mammalian signal recognition particle, three GTP-bin ding motifs in the NH2-terminal half and amphipathic helical cores in the COOH-terminus were conserved. The depletion of ffh in B. subtilis led to growth arrest and drastic morphological changes. Furthermore, t he translocation of beta-lactamase and alpha-amylase under the deplete d condition was also defective.