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J. Virol., 02 1996, 771-777, Vol 70, No. 2
E Schmalzbauer, B Strack, J Dannull, S Guehmann and K Moelling
The nucleocapsid (NC) protein of human immunodeficiency virus type 1 is
required for packaging of viral RNA and for virion assembly. It contains
two clusters of basic amino acids, consisting of five and four amino acid
residues, flanking the first of its two zinc fingers. These amino acid
residues have been mutagenized to neutral ones individually, as well as in
various combinations, by site-directed mutagenesis. Wild- type NCp7 and the
mutant proteins were expressed as recombinant proteins in Escherichia coli,
with six histidines as tags at their amino termini in order to allow
efficient purification. The purified proteins were analyzed for RNA binding
in vitro with human immunodeficiency virus type 1 5' leader RNA transcribed
in vitro. Assays comprised Northwestern blots at various salt
concentrations and filter binding tests which allowed determination of the
dissociation constants of the various mutants. The results indicated that
mutations of the amino acid R-7 and of R-32 and K-33 were more critical for
RNA binding than other mutations. Mutation of the other amino acid residues
reduced the binding affinity in proportion to the number of mutations.
Mutation of seven of the nine basic amino acid residues reduced the binding
of RNA by 50- to 90-fold.
Copyright © 1996, American Society for Microbiology
Mutations of basic amino acids of NCp7 of human immunodeficiency virus type 1 affect RNA binding in vitro
Institut fur Medizinische Virologie, Universitat Zurich, Switzerland.
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