A polymeric immunoglobulin receptor-like milk protein with inhibitory activity on human immunodeficiency virus type 1 reverse transcriptase.
A protein with a molecular mass of 85 kDa and an N-terminal sequence resembling polymeric immunoglobulin receptor has been isolated from bovine milk. The isolation procedure involved removal of globulin from acid whey by precipitation with 1.8 M (NH(4))(2)SO(4) followed by addition of (NH(4))(2)SO(4) to attain a concentration of 3.6 M. Subsequent steps included chromatography on CM-Sepharose and Mono S and elution of the protein of interest with a linear NaCl concentration gradient. The polymeric immunoglobulin receptor-like milk protein inhibited HIV-1 reverse transcriptase (RT) with an IC(50) of 4.8 microM. However, it did not exhibit ribonuclease activity. Neither did it inhibit translation in a cell-free rabbit reticulocyte lysate system.