Monoclonal antibody to the amino-terminal L sequence of murine leukemia virus glycosylated gag polyproteins demonstrates their unusual orientation in the cell membrane.

To analyze cell surface murine leukemia virus gag protein expression, we have prepared monoclonal antibodies against the spontaneous AKR T lymphoma KKT-2. One of these antibodies, 43-13, detects an AKR-specific viral p12 determinant. A second monoclonal antibody, 43-17, detects a novel murine leukemia virus-related antigen found on glycosylated gag polyproteins (gp95gag, gp85gag, and gp55gag) on the surface of cells infected with and producing ecotropic endogenous viruses, but does not detect antigens within these virions. The 43-17 antibody immunoprecipitates the precursor of the cell surface gag protein whether in its glycosylated or unglycosylated state, but does not detect the cytoplasmic precursor of the virion gag proteins (Pr65gag). Based on these findings, we have localized the 43-17 determinant to the unique amino-terminal part of the glycosylated gag polyprotein (the L domain). We have determined that gp95gag contains L-p15-p12-p30-p10 determinants, whereas gp85gag lacks the carboxyterminal p10 determinant, and gp55gag lacks both p30 and p10 carboxy terminal determinants. Analysis of cell surface gag expression with the 43-17 antibody leads us to propose that the L domain plays a crucial role in (i) the insertion and orientation of murine leukemia virus gag polyproteins in the cell membrane and (ii) the relative abundance of expression of AKR leukemia virus versus Moloney murine leukemia virus glycosylated gag polyproteins in infected cells.

Isolation of molecules recognized by monoclonal antibodies and antisera: the solid phase immunoisolation technique.

A simple technique for the isolation of antigens recognized by antisera and monoclonal antibodies has been developed. This method, the solid-phase immunoisolation technique, employs the protein-binding properties of polyvinylchloride microtiter plates. Antibodies are adsorbed to the plates either directly or via an anti-immunoglobulin reagent. Antigen is then placed in the wells, and allowed to adsorb to the antibody. The well is washed, and the antigen is then eluted with a denaturing electrophoresis sample buffer for one- or two-dimensional analysis. The solid-phase immunoisolation technique has been used to isolate a variety of cell membrane antigens with high signals and low backgrounds. The ease of the procedure and the high signal-to-noise ratio make this method preferable to the use of a staphylococcal adsorbent for many applications.

Hooked trichomes: a physical plant barrier to a major agricultural pest.

Hooked epidermal appendages (trichomes) on leaves of field bean cultivars effectively capture nymph and adult leafhoppers. Frequency of capture and capture mortality are highly correlated with trichome density. Hooked trichomes inserted at angles less than 30 degrees are ineffective in capture.