Gene organization of the Streptococcus pyogenes plasmid pDB101: sequence analysis of the orf eta-copS region

The gene organization of the broad-host-range low-copy-number pSM19035-derived plasmid pDB101 is presented. Analysis of the 19,202-bp sequence revealed thirteen different open reading frames (orfs). Nine of these orfs (repS-orf-orf beta-orf gamma-orf delta-orf epsilon-orf zeta-erm2-erm1 have been previously identified [Cegłowski et al., Gene 136 (1993) 1-12]. The extraordinarily long inverted repeated sequence, which includes orf alpha-orf beta-orf gamma-orf delta-orf epsilon-orf zeta, comprises 76% of the pDB101 molecule. The gene order in pDB101 is repS-orf alpha-orf beta-orf gamma-orf delta-orf epsilon-orf zeta-erm2-erm1-orf zeta-orf epsilon-orf delta-orf gamma-orf beta-orf alpha-orf eta-orf theta-orf1-copS. The organization of genes of the orf eta-orf gamma region resembles the organization of genes in the orfA-orfI region of pAM beta 1. Except for Orf1, bands of radioactive proteins corresponding to the molecular mass of the deduced reading frames (26.7, 14.3 and 10.3 kDa) were detected using the T7 promoter-expression system. The orf1 encoded a product (deduced molecular mass 28.3 kDa) which shows anomalous electrophoretical mobility corresponding to 60 kDa. The copS- and orf1-encoded proteins share homology to plasmid copy number control systems and Gram+ cocci surface proteins, respectively. The orf eta and orf theta encode proteins with unknown activity.