[Complete nucleotide sequence and analysis of Planobispora linear plasmid pPR2].
OBJECTIVE
To obtain the complete nucleotide sequence of Planobispora linear plasmid pPR2, and reveal the novel telomere replication protein and possible replication loci from the centrally located origin.


METHODS
We cloned the EcoRI DNA fragments and assembled them to get the whole sequence of pPR2. We analyzed the secondary structure of the telomere DNA and the putative telomere replication protein using software, and detected the possible replication loci by Streptomyces protoplast transformation.


RESULTS
The complete nucleotide sequence of pPR2 consists of 15520 bp in length, with a 68.1% (G+C) content. The 329 bp terminal inverted repeat sequence can't form the conserved fold-back secondary structure as that of many Streptomyces linear replicons. Lacking of typical Streptomyces tap/tpg locus for telomere replication, pPR2.3c encodes a protein with two domains resembling the telomere associated protein of Streptomyces and helicase of Haemophilus respectively. No typical Streptomyces iteron-rep locus for replication from the centrally located origin, two DNA fragments containing almost all pPR2 were cloned and introduced by transformation into S. lividans ZX7, but no transformants were obtained. pPR2 encodes single-strand binding protein which may regulate replication of linear DNA and Tra protein for conjugation transfer in actinomycetes.


CONCLUSIONS
pPR2 is the smallest actinomycete linear plasmid beyond Streptomyces. This is the first time to report the complete nucleotide sequence of linear plasmid in the genus Planobispora. pPR2 may have novel mechanism for telomere replication, and pPR2.2c and pPR2.3c encode the possible telomere replication proteins.
Yang
Yong
Y
Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China. yyang@sibs.ac.cn
Qin
Zhongjun
Z
D039903:Actinobacteria / Q000737:chemistry* / Q000201:enzymology / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D001482:Base Composition; D020029:Base Pairing; D001483:Base Sequence; D004261:DNA Replication; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D010957:Plasmids / Q000737:chemistry* / Q000235:genetics*
D001426:Bacterial Proteins; D004269:DNA, Bacterial