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Journal of Virology, May 2000, p. 4710-4720, Vol. 74, No. 10
Departments of Molecular
Biology1 and
Chemistry,2 The Scripps Research
Institute, La Jolla, California 92037
Received 8 November 1999/Accepted 18 February 2000
Feline immunodeficiency virus (FIV) protease is structurally very
similar to human immunodeficiency virus (HIV) protease but exhibits
distinct substrate and inhibitor specificities. We performed mutagenesis of subsite residues of FIV protease in order to define interactions that dictate this specificity. The I37V, N55M, M56I, V59I,
and Q99V mutants yielded full activity. The I37V, N55M, V59I, and Q99V
mutants showed a significant increase in activity against the HIV-1
reverse transcriptase/integrase and P2/nucleocapsid junction peptides
compared with wild-type (wt) FIV protease. The I37V, V59I, and Q99V
mutants also showed an increase in activity against two rapidly cleaved
peptides selected by cleavage of a phage display library with HIV-1
protease. Mutations at Q54K, I98P, and L101I dramatically reduced
activity. Mutants containing a I35D or I57G substitution showed no
activity against either FIV or HIV substrates. FIV proteases all failed
to cut HIV-1 matrix/capsid, P1/P6, P6/protease, and protease/reverse
transcriptase junctions, indicating that none of the substitutions were
sufficient to change the specificity completely. The I37V, N55M, M56I,
V59I, and Q99V mutants, compared with wt FIV protease, all showed
inhibitor specificity more similar to that of HIV-1 protease. The data
also suggest that FIV protease prefers a hydrophobic P2/P2' residue
like Val over Asn or Glu, which are utilized by HIV-1 protease, and
that S2/S2' might play a critical role in distinguishing FIV and HIV-1 protease by specificity. The findings extend our observations regarding
the interactions involved in substrate binding and aid in the
development of broad-based inhibitors.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Alteration of Substrate and Inhibitor Specificity
of Feline Immunodeficiency Virus Protease
*
Corresponding author. Mailing address: Department of
Molecular Biology, The Scripps Research Institute, 10550 N. Torrey
Pines Rd., La Jolla, CA 92037. Phone: (858) 784-8270. Fax: (858)
784-2750. E-mail: jelder{at}scripps.edu.
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