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J Virol, June 1998, p. 4956-4961, Vol. 72, No. 6
Division of Cellular and Gene Therapies,
Received 9 September 1997/Accepted 2 March 1998
Human cells express distinct but related receptors for the gibbon
ape leukemia virus (GALV) and the amphotropic murine leukemia virus
(A-MuLV), termed Pit1 and Pit2, respectively. Pit1 is not able to
function as a receptor for A-MuLV infection, while Pit2 does not confer
susceptibility to GALV. Previous studies of chimeric receptors
constructed by interchanging regions of Pit1 and Pit2 failed to clarify
the determinants unique to Pit2 which correlate with A-MuLV receptor
function. In order to identify which regions of Pit2 are involved in
A-MuLV receptor function, we exchanged the putative second and third
extracellular domains of Pit1, either individually or together, with
the corresponding regions of Pit2. Our functional characterization of
these receptors indicates a role for the putative second extracellular
domain (domain II) in A-MuLV infection. We further investigated the
influence of domain II with respect to A-MuLV receptor function by
performing site-specific mutagenesis within this region of Pit2. Many
of the mutations had little or no effect on receptor function. However, the substitution of serine for methionine at position 138 (S138M) in a
Pit1 chimera containing domain II of Pit2 resulted in a 1,000-fold reduction in A-MuLV receptor function. Additional mutations made within
domain II of the nonfunctional S138M mutant restored receptor function
to nearly wild-type efficiency. The high degree of tolerance for
mutations as well as the compensatory effect of particular substitutions observed within domain II suggests that an element of
secondary structure within this region plays a critical role in the
interaction of the receptor with A-MuLV.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Entry of Amphotropic Murine Leukemia Virus Is
Influenced by Residues in the Putative Second Extracellular
Domain of Its Receptor, Pit2
*
Corresponding author. Mailing address: FDA, CBER,
HFM-530, 8800 Rockville Pike, Bethesda, MD 20892. Phone: (301)
827-0481. Fax: (301) 827-0449. E-mail:
wilsonc{at}A1.cber.fda.gov.
J Virol, June 1998, p. 4956-4961, Vol. 72, No. 6
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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