Open Reading Frame III of Borna Disease Virus Encodes a Nonglycosylated Matrix Protein

Abstract

The open reading frame III of Borna disease virus (BDV) codes for a protein with a mass of 16 kDa, named p16 or BDV-M. p16 was described as an N-glycosylated protein in several previous publications and therefore was termed gp18, although the amino acid sequence of p16 does not contain any regular consensus sequence for N glycosylation. We examined glycosylation of p16 and studied its membrane topology using antisera raised against peptides, which comprise the N and the C termini. Neither an N-nor a C-terminal peptide is cleaved from p16 during maturation. Neither deglycosylation of p16 by endoglycosidases nor binding of lectin to p16 was detectable. Introduction of typical N-glycosylation sites at the proposed sites of p16 failed in carbohydrate attachment. Flotation experiments with membranes of BDV-infected cells on density gradients revealed that p16 is not an integral membrane protein, since it can be dissociated from membranes. Our experimental data strongly suggest that p16 is a typical nonglycosylated matrix protein associated at the inner surface of the viral membrane, as is true for homologous proteins of other members of the Mononegavirales order.

Crystal structure of the Borna disease virus matrix protein (BDV-M) reveals ssRNA binding properties

“…The dominant form of BDV-M isolated from infected horses is tetrameric (15), suggesting that it is the tetramer that binds to the viral membrane, and flotation experiments have shown that BDV-M binds to membranes of BDV-infected cells (14). The interaction of the purified BDVM tetramer with brain polar lipid extract was studied by using the monolayer technique (25).…”

“…BDV-M, the M-protein of BDV, is the smallest M-protein (16.2 kDa) among all NSVs. It is located beneath the viral envelope and associates with the inner layer of the viral membrane and as such is responsible for the structural integrity and individual form of virus particles by bridging the nucleocapsid and the envelope (14). BDV-M forms oligomers both in vivo and in vitro, with tetramers as the most stable structural unit (15,16).…”

Lassa Virus Z Protein Is a Matrix Protein Sufficient for the Release of Virus-Like Particles

“…The nature and strength of the membrane binding of Z were examined by various well-established membrane detachment procedures by using either sodium bicarbonate buffer at pH 10 or 2 M KCl or 50 mM EDTA before the treated samples were subjected to flotation analysis as described previously (20,21). However, none of these treatments, which characteristically remove most peripheral membrane proteins, disrupted the association of Z protein with membranes (Fig.…”

Generation and Characterization of a Recombinant Vesicular Stomatitis Virus Expressing the Glycoprotein of Borna Disease Virus

“…BDV was originally identified as the causative agent of Borna disease, an often fatal immune-mediated neurological disease naturally occurring mainly in horses and sheep within regions of endemicity in central Europe (31). Current epidemiological data, however, indicate that the natural host range, prevalence, and geographic distribution of BDV are broader than originally thought (8,16,20,29). Experimentally, BDV has a wide host range, from birds to rodents and nonhuman primates (8,10,16,20,29).…”

“…Experimentally, BDV has a wide host range, from birds to rodents and nonhuman primates (8,10,16,20,29). Both host and viral factors contribute to a variable period of incubation and significant heterogeneity in the symptoms and pathology associated with infection (8,10,16,20,29).BDV is an enveloped virus with a nonsegmented negativestrand RNA genome with a characteristic mononegavirales organization (4, 34, 35). However, based on its unique genetics and biological features, BDV is considered to be the prototypic member of a new virus family, Bornaviridae, within the order Mononegavirales.…”