title: Charged assembly helix motif in murine leukemia virus capsid: an important region for virus assembly and particle size determination.
abstract: We have identified a region near the C terminus of capsid (CA) of murine leukemia virus (MLV) that contains many charged residues. This motif is conserved in various lengths in most MLV-like viruses. One exception is that spleen necrosis virus (SNV) does not contain a well-defined domain of charged residues. When 33 amino acids of the MLV motif were deleted to mimic SNV CA, the resulting mutant produced drastically reduced amounts of virions and the virions were noninfectious. Furthermore, these viruses had abnormal sizes, often contained punctate structures resembling those in the cell cytoplasm, and packaged both ribosomal and viral RNA. When 11 or 15 amino acids were deleted to modify the MLV CA to resemble those from other gammaretroviruses, the deletion mutants produced virions at levels comparable to those of the wild-type virus and were able to complete one round of virus replication without detectable defects. We generated 10 more mutants that displayed either the wild-type or mutant phenotype. The distribution of the wild-type or mutant phenotype did not directly correlate with the number of amino acids deleted, suggesting that the function of the motif is determined not simply by its length but also by its structure. Structural modeling of the wild-type and mutant proteins suggested that this region forms alpha-helices; thus, we termed this motif the "charged assembly helix." This is the first description of the charged assembly helix motif in MLV CA and demonstration of its role in virus budding and assembly.
authors.affiliation: HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland 21702, USA.
authors.forename: Sara Rasmussen
authors.initials: SR
authors.lastname: Cheslock
authors.forename: Dexter T K
authors.initials: DT
authors.lastname: Poon
authors.forename: William
authors.initials: W
authors.lastname: Fu
authors.forename: Terence D
authors.initials: TD
authors.lastname: Rhodes
authors.forename: Louis E
authors.initials: LE
authors.lastname: Henderson
authors.forename: Kunio
authors.initials: K
authors.lastname: Nagashima
authors.forename: Connor F
authors.initials: CF
authors.lastname: McGrath
authors.forename: Wei-Shau
authors.initials: WS
authors.lastname: Hu
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002213:Capsid / Q000737:chemistry* / Q000378:metabolism; D002415:Cats; D004285:Dogs; D017988:Gammaretrovirus / Q000235:genetics / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D009052:Leukemia Virus, Murine / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D013329:Structure-Activity Relationship; D014771:Virion / Q000502:physiology; D019065:Virus Assembly; D014779:Virus Replication