2g34
Human hepatitis B virus T=4 capsid strain adyw complexed with assembly effector HAP1
Structural highlights
FunctionCAPSD_HBVD1 Self assembles to form an icosahedral capsid. Most capsid appear to be large particles with a icosahedral symmetry of T=4 and consist of 240 copies of capsid protein, though a fraction forms smaller T=3 particles consisting of 180 capsid proteins. Entering capsid are transported along microtubules to the nucleus. Phosphorylation of the capsid is thought to induce exposure of nuclear localization signal in the C-terminal portion of the capsid protein that allows binding to the nuclear pore complex via the importin (karyopherin-) alpha and beta. Capsids are imported in intact form through the nuclear pore into the nuclear basket, where it probably binds NUP153. Only capsids that contain the mature viral genome can release the viral DNA and capsid protein into the nucleoplasm. Immature capsids get stucked in the basket. Capsids encapsulate the pre-genomic RNA and the P protein. Pre-genomic RNA is reverse transcribed into DNA while the capsid is still in the cytoplasm. The capsid can then either be directed to the nucleus, providing more genome for transcription, or bud through the endoplasmic reticulum to provide new virions (By similarity).[1] Encapsidates hepatitis delta genome (By similarity).[2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedHepatitis B virus (HBV) is a leading cause of liver disease and hepatocellular carcinoma; over 400 million people are chronically infected with HBV. Specific anti-HBV treatments, like most antivirals, target enzymes that are similar to host proteins. Virus capsid protein has no human homolog, making its assembly a promising but undeveloped therapeutic target. HAP1 [methyl 4-(2-chloro-4-fluorophenyl)-6-methyl-2-(pyridin-2-yl)-1,4-dihydropyrimidin e-5-carboxylate], a heteroaryldihydropyrimidine, is a potent HBV capsid assembly activator and misdirector. Knowledge of the structural basis for this activity would directly benefit the development of capsid-targeting therapeutic strategies. This report details the crystal structures of icosahedral HBV capsids with and without HAP1. We show that HAP1 leads to global structural changes by movements of subunits as connected rigid bodies. The observed movements cause the fivefold vertices to protrude from the liganded capsid, the threefold vertices to open, and the quasi-sixfold vertices to flatten, explaining the effects of HAP1 on assembled capsids and on the assembly process. We have identified a likely HAP1-binding site that bridges elements of secondary structure within a capsid-bound monomer, offering explanation for assembly activation. This site also interferes with interactions between capsid proteins, leading to quaternary changes and presumably assembly misdirection. These results demonstrate the plasticity of HBV capsids and the molecular basis for a tenable antiviral strategy. Global structural changes in hepatitis B virus capsids induced by the assembly effector HAP1.,Bourne CR, Finn MG, Zlotnick A J Virol. 2006 Nov;80(22):11055-61. Epub 2006 Aug 30. PMID:16943288[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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