1cd3: Difference between revisions

[[Image:1cd3.gif|left|200px]]<br /><applet load="1cd3" size="350" color="white" frame="true" align="right" spinBox="true"  

An empty precursor particle called the procapsid is formed during assembly of the single-stranded DNA bacteriophage phiX174. Assembly of the phiX174 procapsid requires the presence of the two scaffolding proteins, D and B, which are structural components of the procapsid, but are not found in the mature virion. The X-ray crystallographic structure of a "closed" procapsid particle has been determined to 3.5 A resolution. This structure has an external scaffold made from 240 copies of protein D, 60 copies of the internally located B protein, and contains 60 copies of each of the viral structural proteins F and G, which comprise the shell and the 5-fold spikes, respectively. The F capsid protein has a similar conformation to that seen in the mature virion, and differs from the previously determined 25 A resolution electron microscopic reconstruction of the "open" procapsid, in which the F protein has a different conformation. The D scaffolding protein has a predominantly alpha-helical fold and displays remarkable conformational variability. We report here an improved and refined structure of the closed procapsid and describe in some detail the differences between the four independent D scaffolding proteins per icosahedral asymmetric unit, as well as their interaction with the F capsid protein. We re-analyze and correct the comparison of the closed procapsid with the previously determined cryo-electron microscopic image reconstruction of the open procapsid and discuss the major structural rearrangements that must occur during assembly. A model is proposed in which the D proteins direct the assembly process by sequential binding and conformational switching.

1CD3 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Enterobacteria_phage_phix174 Enterobacteria phage phix174]. The following page contains interesting information on the relation of 1CD3 with [[http://pdb.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb2_1.html Bacteriophage phiX174]]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1CD3 OCA].  

[[Category: Rossmann, M G.]]

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