M. Gani et al., MONOCLONAL-ANTIBODIES AGAINST PROGESTERONE - EFFECT OF STEROID-CARRIER COUPLING POSITION ON ANTIBODY SPECIFICITY, Journal of steroid biochemistry and molecular biology, 48(2-3), 1994, pp. 277-282
Monoclonal anti-progesterone antibodies were raised by immunizing mice
with progesterone coupled through either the C3, C6 or C11 positions
to protein carrier (bovine serum albumin, BSA). The specificity of fou
r antibodies for a range of steroids related to progesterone, some car
rying substitutions at various ring positions, was studied by competit
ive inhibition in an ELISA system. The results demonstrated that the r
ing coupling position has a determining effect on the cross-reactivity
of the antibodies obtained. The patterns of cross-reaction were inter
preted in the light of the structure of the combining site of an anti-
progesterone antibody (DB3) recently determined by X-ray crystallograp
hy, and inferences drawn about the orientation of steroid in the combi
ning sites of the antibodies studied. Specifically, in two antibodies
raised against progesterone-11-BSA, the orientation of steroid resembl
ed that of the progesterone-DB3 complex, with positions C11 and C3 exp
osed and C6 and C20 buried; an antibody raised against progesterone-6-
BSA bound steroid in an apparently similar disposition, except that C6
was exposed and C11 buried; finally, in an antibody raised against pr
ogesterone-3-BSA, all steroid positions other than C3 were apparently
buried in the steroid-antibody complex.