New genes involved in Yersinia pestis fraction I biosynthesis

Antigenic and immunochemical properties of Yersinia pestis fraction I (FI) preparations extracted by different methods were studied with polyclonal an d monoclonal antibodies. The existence of mature 171 in a form of a complex antigen whose subunits have different genetic control was demonstrated. Ga lactolipid was shown, with caf1 product, to be the second species-specific component of the FI complex molecule and is probably encoded by chromosomal genes. It, like caf1 product, was expressed in higher quantities at 37 deg reesC than at 28 degreesC. Among FI subunits there were at least two protei ns of 28 +/- 2 kDa and 43 +/- 2 kDa which were not specific for Y pestis bu t were found also in all Yersinia spp. and some other bacteria. These prote ins were synthesised independently of the incubation temperature (4 degrees -40 degreesC) and are possibly encoded chromosomally but outside the caf o peron and galactolipid-encoding genes. Both proteins together with galactol ipid comprise an envelope antigen found in pFra(-) or plasmidless Y pestis strains. Organisation of pestis FI (mature capsular antigen) in the form of a complex of the envelope antigen and the caf1 product is discussed.