Steroid Binding by Mouse Salivary Proteins

The goals of this study were to determine thesteroid-binding specificity of the mouse salivaryandrogen-binding protein (ABP) family and to ascertainwhether there might be other proteins in mouse saliva capable of binding steroids. The optimalconditions for testosterone binding by mouse salivaryproteins were determined using a small-scalechromatography system to separate bound from unboundsteroid. Testosterone binding appeared to be biphasicbut was directly proportional to saliva concentration,with an optimum temperature of 37 C in the second phase.These results were used to develop a steroid-binding protocol to study the steroid specificity ofsalivary proteins separated by electrophoresis. The ABPfamily bound testosterone and progesterone well andHO-progesterone and DHT to a lesser extent but did not bind either cholesterol or estradiol.Steroid structural comparisons suggest that binding byABP is governed by the A ring of the steroid. Anotherprotein that is not a member of the ABP family bound cholesterol specifically but no protein thatspecifically bound estradiol was observed.