Related Experiment Videos
Identification of a critical basic residue on the ecotropic murine leukemia virus receptor
Zhaohui Qian1, Robin Donald, Hongzhe Wang
1Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
Abstract:
Susceptibility to ecotropic murine leukemia viruses (MLV) is restricted to mice and rats at the level of virus binding to the host cell receptor. Asparagine 232, valine 233, tyrosine 235, and glutamic acid 237 in the third extracellular domain (EL3) of the receptor are critical determinants of the host range difference between mice and humans. However, placing these residues in the human homolog confers only partial binding, indicating that other divergent sequences are involved. We sought to determine if the other sequences lie within or outside EL3. Here we report the identification of lysine 234 as another critical residue that influences virus binding and infection, as well as evidence that the unidentified sequences lie outside EL3. Each of the four basic residues in the third extracellular domain were changed to an acidic residue and initially examined in combination with a change at position 235 or position 237. Substitution of lysine 211, 215, or 222 combined with substitution of the critical tyrosine 235 or glutamic acid 237 did not affect virus infection. However, combined substitution of lysine 234, a conserved residue between mice and humans, and tyrosine 235 resulted in a marked decrease in virus infection and binding. A lysine 234 change alone reduced virus binding, contrary to previous observations that at least two of the other four residues must be changed before binding is reduced. Interestingly, there was no decrease in infection when lysine 234 was replaced in combination with glutamic acid 237. This result suggests that residue 234 may act by influencing the local structure of residues 233 to 235, whereas the presence of a glycine at position 236 may prevent this influence from extending to residue 237. With this report, the involvement of all the residues divergent between mice and humans in the third extracellular domain has been ruled out, suggesting that as yet unidentified determinants lie in other extracellular domains.
Insights
Murine leukemia virus (MLV) host range is determined by specific receptor residues. Lysine 234 was identified as a critical determinant influencing MLV binding and infection, with other factors located outside the third extracellular domain.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Susceptibility to ecotropic murine leukemia viruses (MLV) is a species-specific trait.
- The viral receptor's third extracellular domain (EL3) contains key residues (Asn232, Val233, Tyr235, Glu237) influencing host range differences between mice and humans.
- Previous studies indicated partial binding with human homologues, suggesting additional determinants.
Purpose of the Study:
- To identify additional residues within or outside EL3 that contribute to MLV host range specificity.
- To investigate the role of lysine 234 in MLV binding and infection.
Main Methods:
- Site-directed mutagenesis of the viral receptor's EL3.
- Assays to measure MLV binding and infection rates.
- Analysis of specific residue substitutions and their combined effects.
Main Results:
- Lysine 234 was identified as a critical residue affecting MLV binding and infection, independent of other known determinants.
- Substitution of lysine 234 alone significantly reduced MLV binding, contrary to prior findings.
- The combined substitution of lysine 234 and tyrosine 235 markedly decreased MLV infection and binding.
- The influence of lysine 234 appears localized, potentially due to glycine at position 236.
Conclusions:
- All divergent residues within the third extracellular domain have been excluded as sole determinants of MLV host range.
- Lysine 234 plays a significant role in MLV binding and infection.
- Unidentified determinants of MLV host range likely reside in other extracellular domains of the receptor.