期刊
JOURNAL OF VIROLOGY
卷 80, 期 1, 页码 161-171出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/JVI.80.1.161-171.2006
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资金
- NCI NIH HHS [R01 CA029303, CA29303] Funding Source: Medline
- NIAID NIH HHS [T32 AI07640, T32 AI007640] Funding Source: Medline
- NATIONAL CANCER INSTITUTE [R01CA029303] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES [T32AI007640] Funding Source: NIH RePORTER
Cylindrical projections surrounding the fivefold-symmetry axes in minute virus of mice (MVM) harbor central pores that penetrate through the virion shell. In newly released DNA-containing particles, these pores contain residues 28 to 38 belonging to a single copy of VP2, disposed so that its extreme N-terminal domain projects outside the particle. Virions are metastable, initially sequestering internally the N termini of all copies of the minor capsid protein, VP1, that is essential for entry. This VP1 domain can be externalized in vitro in response to limited heating, and we show here that the efficiency of this transition is greatly enhanced by proteolysis of VP2 N termini to yield VP3. This step also renders the VP1 rearrangement pH dependent, indicating that VP2 cleavage is a maturation step required to prime subsequent emergence of the VP1 entry domain. The tightest constriction within the cylinder is created by VP2 leucine 172, the five symmetry-related copies of which form a portal that resembles an iris diaphragm across the base of the pore. In MVMp, threonine substitution at this position, L172T, yields infectious particles following transfection at 37 degrees C, but these can initiate infection only at 32 degrees C, and this process can be blocked by exposing virions to a cellular factor(s) at 37 degrees C during the first 8 h after entry. At 32 degrees C, the mutant particle is highly infectious, and it remains stable prior to VP2 cleavage or following cleavage at pH 5.5 or below. However, upon exposure to neutral pH following VP2 cleavage, its VP1-specific sequences and genome are extruded even at room temperature, underscoring the significance of the VP2 cleavage step for MVM particle dynamics.
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