Here, we report the primary structure of hortensin 4, main type 1 ribosome inactivating protein (RIP) isolated from Atriplex hortensis seeds. The complete sequencing was achieved by a combination of mass spectrometry coupled with Edman degradation. The amino acid sequence of hortensin 4 matches with that of Atriplex patens type 1 RIP, deduced from the cDNA sequence (AC: ABJ90432.1). The protein consists of 254 amino acid residues, without cysteinyl residues and a N-Acetylhexosamine chain at position Asn231. Structural studies (CD spectrum and 3D model) show a protein core typical of RIPs, and the amino acid residues of active site are conserved. In addition, to get insight into the protective effects of hortensin 4 against pathogens and its putative biotechnological applications, we evaluated the: i) N-glycosylase activity against the tobacco mosaic virus (TMV) RNA
(ii) antifungal activity towards Trichoderma harzianum and Botrytis cinerea, by damaging fungal ribosomes
and (iii) inhibition of human primary glioblastoma NULU cells proliferation, with cytotoxicity enhanced in the presence of temozolomide, used as a chemotherapeutic agent. Altogether, the multiple biological activities of hortensin 4 could be exploited both to improve the resistance to various pathogens by engineering transgenic plants and to develop useful tools for cancer therapy.