1al0
From Proteopedia
PROCAPSID OF BACTERIOPHAGE PHIX174
Structural highlights
Function[B_BPPHX] Participates in the assembly of the viral procapsid in the cytoplasm. Forms first a 12S pre-assembly complex with protein H, and F and G pentamers, then twelve 12S complexes are joined by the D protein to form the procapsid. Internal scaffold protein B is released from the procapsid upon genome packaging, possibly through affinity displacement by the protein J, or by proteolysis. [D_BPPHX] Assembles the procapsid by joining twelve 12S pre-assembly complex into a T=1 icosahedral particle, called 108S procapsid. Ten proteins D bind each 12S complex, which are formed by three pentamers of F, G, B protein and a H protein. The scaffolding protein is released from the provirion after genome packaging to form the mature virion.[1] [2] [G_BPPHX] Attaches the circulating virion to the bacterial lipopolysaccharides which serve as receptor for the virus. Determines the phage host-range. Probably triggers with protein H the injection of the phage DNA into the host cytoplasm upon conformational changes induced by the interaction with host lipopolysaccharides.[3] [4] [F_BPPHX] Assembles to form an icosahedral capsid with a T=1 symmetry, about 30 nm in diameter, and consisting of 60 capsid proteins F.[5] 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 PubMedThe assembly of a macromolecular structure proceeds along an ordered morphogenetic pathway, and is accomplished by the switching of proteins between discrete conformations as they are added to the nascent assembly. Scaffolding proteins often play a catalytic role in the assembly process, rather like molecular chaperones. Although macromolecular assembly processes are fundamental to all biological systems, they have been characterized most thoroughly in viral systems, such as the icosahedral Escherichia coli bacteriophage phiX174. The phiX174 virion contains the proteins F, G, H and J. During assembly, two scaffoldingproteins B and D are required for the formation of a 108S, 360-A-diameter procapsid from pentameric precursors containing the F, G and H proteins. The procapsid contains 240 copies of protein D, forming an external scaffold, and 60 copies each of the internal scaffolding protein B, the capsid protein F, and the spike protein G. Maturation involves packaging of DNA and J proteins and loss of protein B, producing a 132S intermediate. Subsequent removal of the external scaffold yields the mature virion. Both the F and G proteins have the eight-stranded antiparallel beta-sandwich motif common to many plant and animal viruses. Here we describe the structure of a procapsid-like particle at 3.5-A resolution, showing how the scaffolding proteins coordinate assembly of the virus by interactions with the F and G proteins, and showing that the F protein undergoes conformational changes during capsid maturation. Structure of a viral procapsid with molecular scaffolding.,Dokland T, McKenna R, Ilag LL, Bowman BR, Incardona NL, Fane BA, Rossmann MG Nature. 1997 Sep 18;389(6648):308-13. PMID:9305849[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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