The “Putative” Leucine Zipper Region of Murine Leukemia Virus Transmembrane Protein (P15e) Is Essential for Viral Infectivity

Abstract

In order to determine the role of the putative leucine zipper region of murine leukemia virus (MLV) transmembrane protein p15E, nine mutations in this region were introduced by site-directed mutagenesis. None of these mutations affected the expression or transport of the envelope protein or incorporation into virions. The mutants were analyzed for their ability to infect NIH3T3 cells and to induce cell fusion in a rat XC cell fusion assay. Mutations removing the charge of the hydrophilic residues reduced infectivity in NIH3T3 cells but had either no effect or a minor effect on envelope-induced XC cell fusion. Six mutations of hydrophobic residues of the putative leucine zipper region were constructed; four completely abolished the ability to infect NIH3T3 cells and these mutant envelopes were also unable to induce cell fusion in the XC cell fusion assay. These data demonstrate the absolute requirement for the putative leucine zipper region for both fusion and infection of MLV.

Sequence variation of koala retrovirus transmembrane protein p15E among koalas from different geographic regions

“…S2) were predicted to drastically change the local surface charge. Such changes in the KoRV p15E domain could have important biological implications, as has been shown for other viruses, where changes in charge surrounded pockets and electrostatic interactions with small molecules were found to affect trimer assembly, membrane fusion, and viral entry (Ramsdale et al, 1996; Zhu et al, 1998). Some of the variants were also identified in museum specimens (Fig.…”

Mutations in the Leucine Zipper Motif and Sterol-sensing Domain Inactivate the Niemann-Pick C1 Glycoprotein

“…The NPC1 domain and sequences immediately downstream from it contain four conserved potential N-glycosylation sites (Asn-70, Asn-122, Asn-185, and Asn-222) in the human and murine proteins. The NPC1 domain also contains a leucine zipper motif (amino acid residues 73-94), similar in structure to motifs that mediate the homo-and heterodimerization of a number of proteins (8,9). Beyond the NPC1 domain lie up to 16 putative transmembrane domains and sequences with strong homology to the sterol-sensing domains of the sterol response elementbinding protein cleavage-activating protein (SCAP), 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, and the Hedgehog signaling protein, Patched (4,6).…”

Suppression of a Fusion Defect by Second Site Mutations in the Ecotropic Murine Leukemia Virus Surface Protein

“…Following virus binding, the envelope protein induces fusion of viral and cellular membranes to release the nucleocapsid into the cytoplasm. Because direct measurement of the fusogenic potential of an envelope protein during viruscell fusion is difficult, indirect cell-cell fusion assays using XC cells have been widely used (3,12,23). XC cells express the ecotropic retrovirus receptor on their surface and are susceptible to MLV infection.…”