Mapping regions of the matrix protein of vesicular stomatitis virus which bind to ribonucleocapsids, liposomes, and monoclonal antibodies

Abstract

The matrix (M) protein of vesicular stomatitis virus (VSV) appears to function as a bridge between the ribonucleocapsid (RNP) core and the envelope in assembly of the virion. Two such properties would necessitate at least one site for interaction with the nucleocapsid and one with the envelope. In this study M protein was found to mediate the in vitro binding to RNP cores of phospholipid vesicles, representing membrane structures. The M protein could bind initially to either the vesicles or the RNP cores to promote RNP-vesicle association. A trypsin-resistant fragment (MT) of M protein, missing the initial 43 amino acids from its amino terminus, reconstituted with acidic phospholipid vesicles with the same binding efficiency as did whole M protein, suggesting that the carboxy-terminal 81% retained those regions of the M protein which interact with a lipid bilayer. The MT protein, however, was considerably less efficient than intact M protein as an inhibitor of in vitro virus transcription; almost 2.5-fold more MT protein than intact M protein was required for 50% inhibition of VSV transcription, indicating that a site for interaction with the RNP core may have been lost. A monoclonal antibody which is able to reverse the in vitro inhibition of transcription by M protein did not react by immunoblotting with MT protein. Partial tryptic digests of the M protein probed with this monoclonal antibody indicated that epitope 1 lies between amino acid residues 18 and 43. This region appears to be a site that promotes interaction of the M protein with the RNP core of VSV. Monoclonal antibodies to epitopes 2 and 3, which exhibit some overlap in binding to M protein but do not reverse transcription inhibition, were mapped by cleavage with N-chlorosuccinimide at regions in a carboxy direction from epitope 1. * Corresponding author. t Present address: Biotherapeutics Incorporated, Franklin, TN 37064.G, and M) take independent paths to the site of virus assembly at the plasma membrane of the infected cell (1,2,6,16,22,23,34); synthesis of M protein is the rate-limiting step in this maturation process (53). Removal of M protein from the RNP core yields a relaxed, highly extended nucleocapsid structure, while condensation of the RNP into a tightly coiled skeleton is mediated through the association of M protein with the nucleocapsid (20,37,38). Appearance of M protein at the cell membrane causes decreased mobility of the already-inserted G protein (46). Protein cross-linking studies with intact virions revealed the formation of G-M and M-N but not G-N heterodimers (18). These studies suggest that M protein functions as a bridge between the cytoplasmic RNP structures and those regions of the cellular membrane into which the G protein has been inserted.The strong interaction between M protein and the RNP core enables M protein to act as an endogenous inhibitor of viral transcription. Transcription reactions with detergentdisrupted whole virions demonstrate a virus-concentrationdependent regulatory effect which was attributed to an ...

Cooperation of an RNA Packaging Signal and a Viral Envelope Protein in Coronavirus RNA Packaging

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Reviewing Chandipura: A Vesiculovirus in Human Epidemics

“…The matrix protein, M lies in the inner surface of the virion to tether core nucleocapsid to the membrane. Highly basic N-terminal domain, with eight lysine residues, enables membrane binding (Ogden et al 1986) and is separated from the rest of the polypeptide by a triple proline sequence (Rose and Gallione 1981). Crystal structure of VSV-M protein revealed contributions from additional domain in membrane association and presence of a flexible link conserved among mononegavirales that provide proper alignment to the membrane binding domain (Gaudier et al 2002).…”

Monoclonal Antibody #3‐9‐16 Recognizes One of the Two Isoforms of Rabies Virus Matrix Protein That Exposes Its N‐Terminus on the Virion Surface

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