A study of the method to pick up a selenocysteine tRNA in Bacillus subtilis

In Bacillus subtilis, selenocysteine tRNA has not been identified in a total genome sequence so far (1). To explore the system of selenocysteine incorporation in B. subtilis, we screened serine-acceptable tRNAs to find an unknown tRNA for selenocysteine by the combined method of specific biotinylation of aa-tRNA (2) and RT-PCR (3). cDNAs obtained from the serine-acceptable tRNA pool were amplified and cloned into plasmid to read its sequence. This procedure gave cDNA library corresponding known serine tRNAs, but no candidate for selenocysteine has been found. Thus, this result, together with the previous data (4), might reveal that there is no selenocysteine tRNA in B. subtilis and/or metabolism of selenium is considerably different from known one as seen in other bacteria.