ABSTRACT
A PCR-based screening method was used to study the genetic variations of the pgm locus among natural isolates of Yersinia pestis from China. Our results indicate that genetic variations in the pgm locus are well correlated with biovars of Y. pestis and plague foci, suggesting that the pgm locus plays a role in Y. pestis adaptation to its environment. The gene encoding two-component regulatory system sensor kinase became a pseudogene in all strains of biovar Orientalis due to a thymidine deletion, while it is intact in all the strains of the other biovars. Only strains from Foci H and L are the same as Yersinia pseudotuberculosis in that they have an intact transmembrane helix in the sensor kinase protein, which is lost in all the other strains because of the 18 bp in-frame deletion. The IS100 element that flanks the 39 terminus of the pgm locus was inserted into the chromosome during the within-species microevolution of Y. pestis, which is absent in strains from Foci G, H and L and also in Y. pseudotuberculosis. This fact indicates that the strains from these three foci are of an older lineage of Chinese Y. pestis. It is this IS100 element's absence that maintained high stability of the pgm locus in the Y. pestis strains from these three foci. The IS285 element insertion in the pigmentation segment and the IS100 element insertion in the downstream flanking region of the pgm locus are only present in strains from Foci H and L. The flanking region outside the 59 terminus of the upstream IS100 element is identical in the strains from these two foci, which is different in the other strains. All of these unique characteristics suggest that they are of a special lineage of Chinese Y. pestis.
Subject(s)
Genes, Bacterial , Yersinia pestis/genetics , Alleles , Base Sequence , China , DNA Transposable Elements , DNA, Bacterial/genetics , Genetic Variation , Genomic Instability , Genomic Islands , Humans , Phenotype , Pigmentation/genetics , Polymerase Chain Reaction , Pseudogenes , Yersinia pestis/classification , Yersinia pestis/isolation & purification , Yersinia pseudotuberculosis/classification , Yersinia pseudotuberculosis/geneticsABSTRACT
The venom of elapid snakes contains a number of small proteins that display a broad spectrum of pharmacological activities. In study on the neurotoxin from the venom gland of Bungarus multicinctus, five cDNA sequences (MNCTL1-a,MNCTL1-b,MNCTL1-c,MNCTL1-d and MNCTL2) encoding two novel proteins were obtained from the total RNA by reverse transcription-polymerase chain reaction. Among them, four sequences (MNCTL1-b,MNCTL1-c,MNCTL1-d and MNCTL2) are at the length of 505 bp, composing of a 32 bp 5'-untranslational region,a 212 bp 3'-untranslational region, and a 261 bp open reading frame which encodes a 20 amino acids of signal peptide and a 65 amino acids of mature peptide. But the sequence of MNCTL1-a has only 481 bp because of a 24 bp deletion in 3'-untranslational region. Comparison between cDNA sequences obtained here and that of cardiotoxin-like protein reported by Chang previously shows a homological value above 95.8%. Computer simulation based on deduced amino acid sequences reveals that both proteins encoded by these cDNAs and cardiotoxin-like protein share similar molecular characters, suggesting their functional similarity. This result implies that multicopy genes existing in the genome of Bungarus multicinctus encode cardiotoxin-like proteins.
