DNA-SEQUENCE AND UNITS OF TRANSCRIPTION OF THE CONJUGATIVE TRANSFER GENE-COMPLEX (TRS) OF STAPHYLOCOCCUS-AUREUS PLASMID PGO1

The conjugative transfer genes of 52-kb staphylococcal R plasmid pGO1 were localized to a single BglII restriction fragment and cloned in Es cherichia coli. Sequence analysis of the 13,612-base transfer region, designated trs, identified 14 intact open reading frames (ORFs), 13 of which were transcribed in the same direction. Each ORF identified was preceded by a typical staphylococcal ribosomal binding sequence, and 10 of the 14 proteins predicted to be encoded by these ORFs were seen when an E. coli in vitro transcription-translation system was used. Fu nctional transcription units were identified in a Staphylococcus aureu s host by complementation of Tn917 inserts that abolished transfer and by Northern (RNA) blot analysis of pGO1 mRNA transcripts. These studi es identified three complementation groups (trsA through trsC, trsD th rough trsK, and trsL-trsM) and four mRNA transcripts (trsA through trs C [1.8 kb], trsA-trsB [1.3 kb], trsL-trsM [1.5 kb], and trsN [400 base s]). No definite mRNA transcript was seen for the largest complementat ion group, trsD through trsK (10 kb). Comparison of predicted trs-enco ded amino acid sequences to those in the data base showed 20% identity of trsK to three related genes necessary for conjugative transfer of plasmids in gram-negative species and 32% identity of trsC to a gene r equired for conjugative mobilization of plasmid pC221 from staphylococ ci.