The translational hop junction and the 5 ' transcriptional start site for the Prevotella loescheii adhesin encoded by plaA

The Prevotella loescheii adhesin gene, plaA, contains a coding gap between a small open reading frame (ORF-I) and a large open reading frame (ORF-2). Translation of the plaA mRNA requires bypassing this 29-nt coding gap on th e plaA transcript. We have determined the N-terminal peptide sequence of th e SO34 adhesin beyond the gap sequence. This sequence shows that the peptid e junction between ORF-1 and ORF-2 is continuous in the adhesin and support s the conclusion that synthesis of the SO34 adhesin occurs by a ribosomal h op mechanism. To elucidate upstream signals, we used the 5' RACE (rapid amp lification of cDNA ends) technique to map the start point of the plaA mRNA. DNA sequencing of plasmids with the 5' RACE products placed the 5' end of plaA mRNA 270 nt upstream from the plaA start codon. A region corresponding to a Bacteroides fragilis promoter consensus sequence precedes this start site.