scholarly journals Functional Characterization of the N Termini of Murine Leukemia Virus Envelope Proteins

2001 ◽  
Vol 75 (9) ◽  
pp. 4357-4366 ◽  
Author(s):  
Chi-Wei Lu ◽  
Monica J. Roth
Keyword(s):  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Functional Characterization ◽  
Virus Titer ◽  
Envelope Proteins ◽  
Virus Envelope ◽  
C Terminus ◽  
N Terminus ◽  
Env Protein ◽  
Murine Leukemia

ABSTRACT The function of the N terminus of the murine leukemia virus (MuLV) surface (SU) protein was examined. A series of five chimeric envelope proteins (Env) were generated in which the N terminus of amphotropic 4070A was replaced by equivalent sequences from ecotropic Moloney MuLV (M-MuLV). Viral titers of these chimeras indicate that exchange with homologous sequences could be tolerated, up to V17eco/T15ampho (crossover III). Constructs encoding the first 28 amino acids (aa) of ecotropic M-MuLV resulted in Env expression and binding to the receptor; however, the virus titer was reduced 5- to 45-fold, indicating a postbinding block. Additional exchange beyond the first 28 aa of ecotropic MuLV Env resulted in defective protein expression. These N-terminal chimeras were also introduced into the AE4 chimeric Env backbone containing the amphotropic receptor binding domain joined at the hinge region to the ecotropic SU C terminus. In this backbone, introduction of the first 17 aa of the ecotropic Env protein significantly increased the titer compared to that of its parental chimera AE4, implying a functional coordination between the N terminus of SU and the C terminus of the SU and/or transmembrane proteins. These data functionally dissect the N-terminal sequence of the MuLV Env protein and identify differential effects on receptor-mediated entry.

scholarly journals Characterizing the Murine Leukemia Virus Envelope Glycoprotein Membrane-Spanning Domain for Its Roles in Interface Alignment and Fusogenicity

2015 ◽  
Vol 89 (24) ◽  
pp. 12492-12500 ◽  
Author(s):  
Daniel J. Salamango ◽  
Marc C. Johnson
Keyword(s):  
Amino Acids ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Tail Domain ◽  
Virus Envelope ◽  
C Terminus ◽  
Viral Glycoproteins ◽  
N Terminus ◽  
Membrane Spanning ◽  
Murine Leukemia

ABSTRACTThe membrane-proximal region of murine leukemia virus envelope (Env) is a critical modulator of its functionality. We have previously shown that the insertion of one amino acid (+1 leucine) within the membrane-spanning domain (MSD) abolished protein functionality in infectivity assays. However, functionality could be restored to this +1 leucine mutant by either inserting two additional amino acids (+3 leucine) or by deleting the cytoplasmic tail domain (CTD) in the +1 leucine background. We inferred that the ectodomain and CTD have protein interfaces that have to be in alignment for Env to be functional. Here, we made single residue deletions to the Env mutant with the +1 leucine insertion to restore the interface alignment (gain of functionality) and therefore define the boundaries of the two interfaces. We identified the glycine-proline pairs near the N terminus (positions 147 and 148) and the C terminus (positions 159 and 160) of the MSD as being the boundaries of the two interfaces. Deletions between these pairs restored function, but deletions outside of them did not. In addition, the vast majority of the single residue deletions regained function if the CTD was deleted. The exceptions were four hydroxyl-containing amino acid residues (T139, T140, S143, and T144) that reside in the ectodomain interface and the proline at position 148, which were all indispensable for functionality. We hypothesize that the hydroxyl-containing residues at positions T139 and S143 could be a driving force for stabilizing the ectodomain interface through formation of a hydrogen-bonding network.IMPORTANCEThe membrane-proximal external region (MPER) and membrane-spanning domains (MSDs) of viral glycoproteins have been shown to be critical for regulating glycoprotein fusogenicity. However, the roles of these two domains are poorly understood. We report here that point deletions and insertions within the MPER or MSD result in functionally inactive proteins. However, when the C-terminal tail domain (CTD) is deleted, the majority of the proteins remain functional. The only residues that were found to be critical for function regardless of the CTD were four hydroxyl-containing amino acids located at the C terminus of the MPER (T139 and T140) and at the N terminus of the MSD (S143 and T144) and a proline near the beginning of the MSD (P148). We demonstrate that hydrogen-bonding at positions T139 and S143 is critical for protein function. Our findings provide novel insights into the role of the MPER in regulating fusogenic activity of viral glycoproteins.

scholarly journals Suppression of Rat Bone Marrow Cells by Friend Murine Leukemia Virus Envelope Proteins

Virology ◽  
1998 ◽  
Vol 242 (2) ◽  
pp. 357-365 ◽  
Author(s):  
Stefan Mazgareanu ◽  
Justus G. Müller ◽  
Stefanie Czub ◽  
Simone Schimmer ◽  
Martin Bredt ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Murine Leukemia Virus ◽  
Bone Marrow Cells ◽  
Leukemia Virus ◽  
Envelope Proteins ◽  
Virus Envelope ◽  
Murine Leukemia ◽  
Rat Bone ◽  
Marrow Cells

scholarly journals Palmitoylation of the Murine Leukemia Virus Envelope Protein Is Critical for Lipid Raft Association and Surface Expression

2002 ◽  
Vol 76 (23) ◽  
pp. 11845-11852 ◽  
Author(s):  
Min Li ◽  
Chinglai Yang ◽  
Suxiang Tong ◽  
Armin Weidmann ◽  
Richard W. Compans
Keyword(s):  
Lipid Rafts ◽  
Lipid Raft ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Viral Fusion ◽  
Deficient Mutant ◽  
Wild Type ◽  
Virus Envelope ◽  
Env Protein ◽  
Murine Leukemia

ABSTRACT To investigate the association of the murine leukemia virus (MuLV) Env protein with lipid rafts, we compared wild-type and palmitoylation-deficient mutant Env proteins by using extraction with the mild detergent Triton X-100 (TX-100) followed by a sucrose gradient flotation assay. We found that the wild-type MuLV Env protein was resistant to ice-cold TX-100 treatment and floated to the top of the gradients. In contrast, we observed that the palmitoylation-deficient mutant Env protein was mostly soluble when extracted by ice-cold TX-100 and stayed at the bottom of the gradients. Both the wild-type and mutant Env proteins were found to be soluble when treated with methyl-β-cyclodextrin before extraction with ice-cold TX-100 or when treated with ice-cold octyl-β-glucoside instead of TX-100. These results indicate that the MuLV Env protein is associated with lipid rafts and that palmitoylation of the Env protein is critical for lipid raft association. Although the palmitoylation-deficient Env mutant was synthesized at a level similar to that of the wild-type Env, it was found to be expressed at reduced levels on the cell surface. We observed syncytium formation activity with both the wild-type and mutant Env proteins, indicating that palmitoylation or raft association is not required for MuLV viral fusion activity.

The nature of the association between the murine leukemia virus envelope proteins

Virology ◽  
1978 ◽  
Vol 91 (2) ◽  
pp. 345-351 ◽  
Author(s):  
Abraham Pinter ◽  
Judy Lieman-Hurwitz ◽  
Erwin Fleissner
Keyword(s):  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Envelope Proteins ◽  
Virus Envelope ◽  
Murine Leukemia
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