Crystallization and X‐ray analysis of the T = 4 particle of hepatitis B capsid protein with an N‐terminal extension
Hepatitis B core (HBc) particles have been extensively exploited as carriers for foreign immunological epitopes in the development of multicomponent vaccines and diagnostic reagents. Crystals of the T = 4 HBc particle were grown in PEG 20 000, ammonium sulfate and various types of alcohols. A temperature jump from 277 or 283 to 290 K was found to enhance crystal growth. A crystal grown using MPD as a cryoprotectant diffracted X‐rays to 7.7 Å resolution and data were collected to 99.6% completeness at 8.9 Å. The crystal belongs to space group P212121, with unit‐cell parameters a = 352.3, b = 465.5, c = 645.0 Å. The electron‐density map reveals a protrusion that is consistent with the N‐terminus extending out from the surface of the capsid. The structure presented here supports the idea that N‐terminal insertions can be exploited in the development of diagnostic reagents, multicomponent vaccines and delivery vehicles into mammalian cells.
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