title: Initiation signals for the conversion of single stranded to double stranded DNA forms in the streptococcal plasmid pLS1.
abstract: We have characterized a region in the streptococcal plasmid pLS1 located between nucleotides 4103 and 4218 which is a signal involved in the conversion of single stranded intermediates of replication to double stranded plasmid forms. This region has a large axis of dyad symmetry resulting in the formation of a secondary structure as revealed by the location of endonuclease S1-cleavage sites in supercoiled covalently closed circular pLS1 DNA. Deletions affecting this region caused a fivefold reduction in plasmid copy number, plasmid instability and the accumulation of single-stranded DNA intermediates. The conversion signal of pLS1 has homologues in other staphylococcal plasmids, sharing a consensus sequence located in the loop of the signal. Computer assisted analysis showed that the signal detected in pLS1 has a high degree of homology with the complementary strand origin of the Escherichia coli single stranded bacteriophages phi X174 and M13.
mesh_terms: D010584:Bacteriophage phi X 174 / Q000235:genetics; D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial / Q000235:genetics*; D004277:DNA, Single-Stranded / Q000235:genetics*; D004720:Endonucleases; D009690:Nucleic Acid Conformation; D010957:Plasmids; D015719:Single-Strand Specific DNA and RNA Endonucleases; D013045:Species Specificity; D013296:Streptococcus pneumoniae / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004720:Endonucleases; D004262:DNA Restriction Enzymes; D015719:Single-Strand Specific DNA and RNA Endonucleases