pVC, a small cryptic plasmid from the environmental isolate of Vibrio cholerae MP-1.
A marine bacterium was isolated from Mai Po Nature Reserve of Hong Kong and identified as Vibrio cholerae MP-1. It contains a small plasmid designated as pVC of 3.8 kb. Four open reading frames (ORFs) are identified on the plasmid, but none of them shows homology to any known protein. Database search indicated that a 440 bp fragment is 96% identical to a fragment found in a small plasmid of another V. cholerae. Further experiments demonstrated that a 2.3 kb EcoRI fragment containing the complete ORF1, partial ORF4 and their intergenic region could self-replicate. Additional analyses revealed that sequence upstream of ORF1 showed the features characteristic of theta type replicons. Protein encoded by ORF1 has two characteristic motifs existed in most replication initiator proteins (Rep): the leucine zipper (LZ) motif located at the N-terminal region and the alpha helix-turn-alpha helix motif (HTH) located at the C-terminal end. The results suggest that pVC replicates via the theta type mechanism and is likely a novel type of theta replicon.
Zhang
Ruifu
R
Laboratory of Environmental Microbiology and Toxicology, Department of Ecology and Biodiversity, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, PR China.
Wang
Yanling
Y
Leung
Pak Chow
PC
Gu
Ji-Dong
JD
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D016000:Cluster Analysis; D004265:DNA Helicases / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics*; D018741:Replication Origin; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators / Q000235:genetics; D014734:Vibrio cholerae / Q000235:genetics* / Q000302:isolation & purification; D014871:Water Microbiology
D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases