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Journal of Virology, December 1999, p. 10164-10172, Vol. 73, No. 12
Department of Microbiology and Immunology,
University of Tennessee
Received 15 April 1999/Accepted 15 September 1999
In the receptor for ecotropic murine leukemia viruses, tyrosine 235 contributes a critical hydrophobic side chain to the virus-receptor interaction (14). Here we report that tryptophan 142 in
ecotropic Moloney murine leukemia virus envelope protein is essential
to virus binding and infection. Replacement of tryptophan 142 by alanine or serine resulted in misfolding. However, replacement by
methionine (W142M) allowed correct folding of the majority of
glycoprotein molecules. W142M virus showed a marked reduction in virus
binding and was almost noninfectious, suggesting that tryptophan 142 is
involved in receptor binding. In contrast, W142Y virus containing a
replacement of tryptophan 142 with an aromatic residue (tyrosine) was
as efficient as wild-type virus in infection and binding of cells
expressing the wild-type receptor. However, W142Y virus was 100-fold
less efficient than wild-type virus in infection of cells expressing a
mutant receptor containing tryptophan instead of the critical tyrosine.
These results strongly support tryptophan 142 being an essential
residue on the virus envelope protein that interacts directly with the
critical hydrophobic residue at position 235 of the ecotropic receptor.
Tryptophan 142 forms one side of a shallow hydrophobic pocket on the
surface of the envelope protein, suggesting that it might comprise the complete putative binding site for tyrosine 235. We discuss the implications of our findings with respect to two models of the envelope
protein trimer. Interestingly, both models place tryptophan 142 at the
interface between adjacent subunits of the trimer.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
A Hydrophobic Patch in Ecotropic Murine Leukemia
Virus Envelope Protein Is the Putative Binding Site for a Critical
Tyrosine Residue on the Cellular Receptor
Memphis, Memphis, Tennessee 38163
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, University of Tennessee
Memphis, 858 Madison Ave., Rm. 101, Memphis, TN 38163. Phone: (901) 448-5521. Fax: (901) 448-8462. E-mail: lalbritton{at}utmem.edu.
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