Fabin, a Novel Calcyon-Like and Glucanase-Like Protein with Mitogenic, Antifungal and Translation-Inhibitory Activities from Broad Beans

A protein with an N-terminal sequence displaying similarities to N-terminal sequences of human calcyon and barley endo-1,4-glucanase, and to C-terminal sequences of human translation initiation factor 4γ and yeast superkiller viralicidic activity, was isolated from the broad bean Vicia faba. The protein, termed fabin, has a molecular mass of 34 kDa in SDS-polyacrylamide gel electrophoresis. Antifungal activity of the protein was observed against several fungal species including Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum and Mycosphaerella arachidicola. Fabin inhibits HIV-1 reverse transcriptase with an IC₅₀ of 34 μM and translation in a rabbit reticulocyte lysate with an IC₅₀ of 2.4 μM. At a concentration of about 1.5 μM fabin is able to elicit a 9-fold increase in the mitogenic response of murine splenocytes.