Heterotetramer composed of two non-covalently linked disulfide-linked heterodimer of chains 1 and 2. Saliva and sebaceous glands. Causes an allergic reaction in human. Binds to IgE. Major allergen produced by the domestic cat. Implicated as an asthma-inducing agent in human. This protein is sticky and easily adheres to walls, carpet, clothing, furniture and bedding. Belongs to the secretoglobin family.