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Related Experiment Videos

Gene encoding the group B streptococcal protein R4, its presence in clinical reference laboratory isolates & R4

B L Smith1, A Flores, J Dechaine

  • 1Departments of Laboratory Medicine & Pathology & Pediatrics, University of Minnesota Medical School & Department of Biology, Luther College, USA.

The Indian Journal of Medical Research
|July 3, 2004
PubMed
Summary

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The R4 protein in group B Streptococcus (GBS) is sensitive to pepsin at pH2, distinguishing it from the similar Rib protein. Genetic analysis confirmed the R4 gene sequence is identical to Rib, aiding in GBS strain identification.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Pathogenesis

Background:

  • R proteins, identified in group B Streptococcus (GBS), exhibit differential protease sensitivity.
  • The R4 protein, prevalent in invasive GBS strains, is trypsin-resistant and pepsin-sensitive at pH2.
  • The Rib protein, similar to R4, has been reported resistant to both proteases.

Purpose of the Study:

  • To identify and characterize the gene encoding the R4 protein from a type III GBS isolate.
  • To compare the genetic and molecular characteristics of R4 with the Rib protein.
  • To develop molecular methods for identifying R4-expressing GBS strains.

Main Methods:

  • Protease sensitivity assays using pepsin under varying pH conditions.
  • Standard hemoglobin assay to assess pepsin activity.

Related Experiment Videos

  • Polymerase Chain Reaction (PCR) and Southern hybridization to screen clinical GBS isolates.
  • Amino acid sequencing of R4 and screening of a GBS genomic library.

    • Main Results:

    • R4 protein demonstrated pepsin sensitivity at pH2 but resistance at pH4, unlike Rib.
    • Pepsin enzymatic activity was confirmed at pH2, highlighting the importance of pH in GBS surface protein assays.
    • Nucleotide sequencing revealed the r4 gene sequence is identical to the rib gene sequence.
    • PCR and Southern techniques successfully identified GBS isolates expressing R4 protein.

    Conclusions:

    • The R4 and Rib proteins share identical nucleotide sequences, confirming their molecular identity.
    • The genetic data supports the differentiation of R4 and Rib proteins based on protease sensitivity.
    • Molecular techniques provide reliable methods for identifying GBS strains based on R protein expression.