Fruticulosina: uma nova proteína inativadora de ribossomos (rip tipo 2) de sementes de Abrus fruticulosus com ação antifúngica e antileishmania

Abstract

The type 2 Ribosome-Inactivating Proteins (type 2 RIPs) are heterodimeric proteins consisting of a RNA-N-glicosydase catalytic subunit linked to a galactose-binding subunit to allow cell surface binding and toxin entry in most mammalian cells, showing a high toxicity. Although their potency to kill cells is remarkable, these RIPs have been explored in the chemical constrution of immunotoxins and diagnostic tools. This work report the isolation, biochemistry characterization, antifungal and antileshimanial action of the fruticulosin, a type 2 RIP of seeds from Abrus fruticulosus. Initially, the fruticulosin was purified by precipitation with ammonium sulfate followed by affinity chromatographic using Sepharose-4B. The protein showed of a single band with an apparent molecular mass of 63 KDa under nonreducing conditions and two bands (30 and 28 KDa, respectively) under reducing conditions, suggesting the presence of disulfide bond. The new RIP strongly agglutinated rabbit erythrocyte and was inhibited by D-galactose, N-acetyl-D-galactosamine and D-lactose. The secondary structure of fruticulosin showed contain predominace of -sheet and tryptophan residues in the most internal regions of the molecule. Moreover, fruticulosin showed high toxicity in vivo on mice (LD50 3.0 μg/kg) and inhibit in vitro protein synthesis by a cell-free system with similar activity to ricin. In addition, fruticulosin showed antifungal activity and exhibited toxic effect on promastigote forms of Leishmania major.