title: Enforcing the positive charge of N-termini enhances membrane interaction and antitumor activity of bovine seminal ribonuclease.
abstract: Binding to cell membrane, followed by translocation into the cytosol and RNA degradation, is a necessary requirement to convert a ribonuclease into a cytotoxin for malignant tumor cells. In this paper, we investigate the membrane binding attitude of bovine seminal ribonuclease (BS-RNase) and its variant G38K-BS-RNase, bearing an enforced cluster of positive charges at the N-termini surface. By using a combination of biophysical techniques, including CD, SPR and ESR, we find for the two proteins a common, two-step mechanism of interaction with synthetic liposomes, an initial binding to the bilayer surface, driven by electrostatic interactions, followed by a shallow penetration in the lipid core. Protein binding effectively perturbs lipid packing and dynamics. Remarkably, the higher G38K-BS-RNase membrane interacting capability well correlates with its increased cytotoxicity for tumor cells. Overall, these studies shed light on the mechanism of membrane binding and perturbation, proving definitely the importance of electrostatic interactions in the cytotoxic activity of BS-RNase, and provide a rational basis to design proteins with anticancer potential.
authors.affiliation: Dipartimento di Chimica Paolo Corradini, Università degli Studi di Napoli Federico II, Via Cintia, 80126 Napoli, Italy.
authors.forename: Gerardino
authors.initials: G
authors.lastname: D'Errico
authors.forename: Carmine
authors.initials: C
authors.lastname: Ercole
authors.forename: Marisa
authors.initials: M
authors.lastname: Lista
authors.forename: Elio
authors.initials: E
authors.lastname: Pizzo
authors.forename: Annarita
authors.initials: A
authors.lastname: Falanga
authors.forename: Stefania
authors.initials: S
authors.lastname: Galdiero
authors.forename: Roberta
authors.initials: R
authors.lastname: Spadaccini
authors.forename: Delia
authors.initials: D
authors.lastname: Picone
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D002417:Cattle; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D004722:Endoribonucleases / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D008051:Lipid Bilayers; D020349:Surface Plasmon Resonance
chemical_list: D000970:Antineoplastic Agents; D008051:Lipid Bilayers; D004722:Endoribonucleases; C032523:ribonuclease SPL