H. Hashiba et al., IDENTIFICATION OF THE REPLICATION REGION OF STREPTOCOCCUS-THERMOPHILUS NO 29 PLASMID PST1, Bioscience, biotechnology, and biochemistry, 57(10), 1993, pp. 1646-1649
The replication region of the 2.77-kilobases (kb) plasmid pST1 from St
reptococcus thermophilus No. 29 was identified. Deletion derivatives o
f pST1 were introduced into plasmid-free S. thermophilus No. 29 and ex
amined for their ability to replicate autonomously. The nucleotide seq
uence had one open reading frame encoded for a 315 amino acid protein
(Rep). Comparisons with proteins encoded by other Gram-positive bacter
ial plasmids strongly suggest that the deduced protein (RepS) encoded
by pST1 has a replicative role. pST1 also contains a DNA sequence simi
lar to the origin nick sequences of pLP1 or pLAB1000, which initiate p
lasmid replication at the plus origin. In a maxicell system, E. coli C
SR603 carrying pSTUC4 produced a protein that was considered to corres
pond to the product of the RepS gene. These results strongly suggest t
hat pST1 is replicated following a rolling-circle mechanism via single
-stranded DNA intermediates.