Structural markers on core protein p30 of murine leukemia virus: functional correlation with Fv-1 tropism.

Abstract

Tryptic peptide maps from more than 50 isolates of murine leukemia virus (MuLV) have shown that, in general, the structure of core protein p30 is highly conserved. However, a structurally variable region of p30 has been identified that is functionally associated with Fv-1 tropism. On the basis of this structural variability, MuLV strains can be classified as B-tropic, N-tropic, xenotropic, and/ MATERIALS AND METHODSThe sources of the MuLV strains utilized in this study are listed in Table 1. Viruses were concentrated and purified from tissue culture media obtained from the third and fourth subcultures by differential centrifugation and banding in 15-50% sucrose gradients, as previously described (11, 13). Virus with a buoyant density of 1.16 g/cm3 was collected and the viral proteins were separated by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (24). Tryptic peptide maps were derived as previously described (1, 13). RESULTSWe have made two-dimensional tryptic peptide maps of the p30 from more than 50 strains of ecotropic, amphotropic, and xenotropic MuLVs isolated from numerous strains of mice. As expected from the NH2-terminal amino acid sequence homology (25), all of the MuLV p3Os displayed a remarkable structural similarity. This indicated that these viruses are all members of a single closely related group, despite their rather wide phenotypic diversity. Fig. 1 upper left is a representative tryptic peptide map of an MuLV p30 from a BALB/c mouse. Twelve peptides have been numbered in Fig. 1 upper right to facilitate subsequent discussion. Some of the lighter spots (e.g., 1, 4, 6, and 9) always appear with a darker spot as a doublet. The spots that appear as doublets (1-2, 4-5, 6-7, 9-10, and 12) could represent the same tyrosine-containing peptide, the darker of the two containing monoiodotyrosine and the lighter one diiodotyrosine (26). As long as labeling and trypsin treatment conditions were held constant, identical peptide maps were generated from the same protein time after time. Several spots or "smudges" were seen in the right half of the MuLV p30 maps. These regions were usually not resolved as discrete spots but showed a similar pattern in most of the maps and were not considered in the comparisons described below.Fine Structural Differences in MuLV p3Os Are Excellent Markers for Specific Viral Strains. Although all MuLV p3Os obviously belong to a single structural group, there are minor differences in the peptide profiles indicative of small variances in the amino acid sequence of these molecules. These differences are reproducibly seen and are thus excellent markers for certain specific MULV strains.

Synthesis of Proviral DNA in Inbred Mouse-derived Clones of Cells Expressing Different Fv-1 Phenotypes

“…The N/D ratio was 0-67 to 0.87 for Ki-MSV rescued by N-tropic virus and 0.38 to 0.49 for Ki-MSV rescued by B-tropic virus (Table 1). This observation is consistent with previous results establishing the Fv-1 determinant as a viral structural protein (p30) (Failer & Hopkins, 1977;Hopkins et al, 1977;Gautsch et al, 1978;Rommelaere et al, 1979;Rassart et al, 1981;Ou et aL, 1983;DesGroseillers & Jolicoeur, 1983) and confirms the phenotypic mixing reported by Rein et al (1976).…”

Autologous Monoclonal Antibodies Recognize Tumour-associated Antigens in X-irradiated C57BL/6 Mice

“…This recombinational origin of RadLVs was indeed confirmed by several authors (Benade et al, 1978;Gautsch et al, 1978;Guillemain et al, 1980;Astier et al, 1982;Rassart et al, 1983). However, RadLV-like agents are detected in only a minority of tumours (Ihle et al, 1976;Erfle et al, 1981).…”

Vif Counteracts a Cyclophilin A-Imposed Inhibition of Simian Immunodeficiency Viruses in Human Cells

“…For instance, Ref1 is expressed in human and other nonmurine cells and imposes a restriction on viral replication similar to that of Fv1 in murine cells (56). Although the precise mechanism of Fv1 restriction remains unclear, the viral determinants for this type of restriction have been mapped to the capsid (CA) protein (21,37). However, Ref1 was found to restrict retroviral replication at a step prior to reverse transcription, while Fv1 seems to impose a post-reverse transcription block (reviewed in reference 22).…”