Table 1.
Features of HIV-1, RSV, PFV and HBV budding strategies.
| Virus species | Retroviroviridae | Hepadnaviridae | ||
|---|---|---|---|---|
| Human Immunodeficiency Virus Type 1 (HIV-1) | Rous Sarcoma Virus (RSV) | Prototype Foamy Virus (PFV) | Hepatitis B virus (HBV) | |
| Glycoprotein organization |
Polyprotein precursor (gp160):
Surface glycoprotein (gp120SU) Transmembrane glycoprotein (gp41TM) |
Polyprotein precursor (gp95): Surface glycoprotein (gp85SU) Transmembrane glycoprotein (gp37TM) |
Polyprotein precursor (gp130): Surface glycoprotein (gp80 SU) Transmembrane glycoprotein (gp48 TM) Leader peptide (gp18LP) |
Hepatitis B surface antigen (HBsAg): Small (S) protein (226aa) Middle (M) protein (226aa + preS2 domain 55aa) Large (L) protein (226aa + preS2 domain 55aa + preS1 domain 108aa or 119aa) |
| Capsid organization |
Gag precursor (Pr55Gag): Matrix (p17MA); Capsid (p24CA); Spacer p2 Nucleocapsid (p7NC); Spacer p1; p6 domain |
Gag-PR precursor (Pr76Gag-PR): Matrix (p17MA); p2a, p2b; pp10; Capsid (p27CA); Spacer; Nucleocapsid (p12NC); Protease (p15PR) |
Gag precursor (p71Gag): p68Gag; p3Gag |
Hepatitis B core protein
(p22HBc): 183-185aa |
| Capsid: membrane targeting domain | Present in MA subunit | Present in MA subunit | No | Not known |
| Budding type |
Type C morphogenesis:
Assembly takes place at the plasma membrane; particle release from plasma membrane or plasma membrane-derived membranes |
Type C morphogenesis:
Assembly takes placeat the plasma membrane; particle release from plasma membrane or plasma membrane-derived membranes |
Type B/D morphogenesis:
Capsid preassembly at the MTOC in the cytoplasm; budding from intracellular membranes (ER/Golgi) and plasma membrane |
Nucleocapsid-formation in cytosol; Budding from intracellular membranes (ER) |
| ESCRT-dependent budding process | Yes ESCRT I, III AIP1/Alix Vps4A/B |
Yes ESCRT II, III AIP1/Alix Vps4A/B |
Yes ESCRT I, III Vps4A/B |
Yes ESCRT II, III Vps4A/B |
| L domain | Gag (p6): PTAP; YPXL |
Gag (p2b): PPPY; LYPSL |
Gag (p71, p68): PSAP |
Core: PPAY; K96? |
| ESCRT interaction partner | Tsg101; AIP1/Alix; | AIP1/Alix; (Nedd4) | Tsg101 | (Nedd4); (γ2-adaptin) |
| Virus like particles | Yes | Yes | No | No, but release of naked capsids |
| Subviral particles | No | No | Yes, low amounts | Yes, high amounts |
| Budding requires | Capsid (Gag) protein only | Capsid (Gag) protein only | Capsid (Gag) and Envelope protein (Env) necessary | Capsid (Core) and Envelope protein (L and S) necessary vDNA synthesis |
| Place of interaction (Capsid-Envelope) | plasma membrane | plasma membrane | trans-Golgi network | ER |
| Pseudotyping | yes | yes | yes, but only with a artificial heterodimerizer system | no |