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1887

Journal of Medical Microbiology logo Journal of Medical Microbiology

Volume 15, Issue 4

The Opacity Factor of Group-A Streptococci No Access

Abstract

SUMMARY

Cell-bound opacity factor (OF) was extracted with sodium dodecyl sulphate (SDS) to yield stable extracts with titres of > 20 000. The mol.-wt distributions of extracellular and SDS-extracted OF, determined by ultrafiltration or chromatography on Sepharose 4B, suggested that the high mol. wt (1 × 10) of extracellular OF is due to aggregation, because cell-bound and extracellular OF in the presence of SDS had an average mol. wt of only 2 × 10.

At least four apparent multiple-molecular forms (mol. wt 7.4-12.0 × 10) of OF were detected by SDS polyacrylamide-gel electro-phoresis. It seemed more probable that these were due to aggregation rather than the existence of different stable conformations. To explain the molecular-size distribution, the subunit would have to be as small as 1 × 10 but this was supported by the finding that OF can be detected after passing through a dialysis membrane provided that its “substrate”, α1-lipoprotein, is present on the other side. This raises the possibility that OF is associated with a carrier molecule.

The isoelectric-focusing profiles of OF were complex and differed markedly with the method used to prepare OF. Extracellular OF had a simple profile with an isoelectric point of 4.0, whereas Triton-extracted OF was the most complex and formed three peaks, the position of which varied depending on whether the detergent was present or absent during focusing runs.

  • Received:
  • Accepted:
  • Published Online:
© 1982 Pathological Society of Great Britain and Ireland
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1982-11-01
2025-01-25
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/content/journal/jmm/10.1099/00222615-15-4-451
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The Opacity Factor of Group-A Streptococci
J. Med. Microbiol. 15, 451 (1982); https://doi.org/10.1099/00222615-15-4-451
/content/journal/jmm/10.1099/00222615-15-4-451
/content/journal/jmm/10.1099/00222615-15-4-451
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