View source for 1kxa

[[Image:1kxa.gif|left|200px]]<br /><applet load="1kxa" size="350" color="white" frame="true" align="right" spinBox="true" 
caption="1kxa, resolution 3.1&Aring;" />
'''SINDBIS VIRUS CAPSID, (WILD-TYPE) RESIDUES 106-264, TETRAGONAL CRYSTAL FORM'''<br />

==Overview==
Sindbis virus core protein (SCP) has been isolated from virus and, crystallized. The X-ray crystallographic structure showed that the, amino-terminal 113 residues appeared to be either disordered or truncated, during crystallization and that the carboxy-terminal residues 114 to 264, had a chymotrypsin-like structure. The carboxy-terminal residues 106 to, 264 and 106 to 266 of SCP have now been expressed in Escherichia coli., Most crystal forms of the truncated proteins were isomorphous with those, of the virally extracted protein. There are only small structural, differences between the truncated recombinant protein and the ordered part, of the wild-type virus-extracted protein. Hence, E. coli-expressed SCP can, be used to study proteolytic properties and the contribution of SCP to, nucleocapsid assembly, interaction with the E2 glycoprotein and, interaction with RNA. The same dimer that was found in two different, crystal forms of the virus-extracted SCP was present also in some of the, crystals of the truncated recombinant protein. The monomer-monomer, interface is maintained by two pairs of hydrogen bonds and by hydrophobic, interactions. Removal of the hydrogen bonds by single substitutions did, not prevent dimer formation. However, a mutation that reduced the, hydrophobic contacts did inhibit dimer formation. The wild-type truncated, SCP is active in E. coli, as evidenced by proteolytic processing of a, series of progressively longer precursors that extend beyond residue 264., Unlike the virus-extracted capsid protein, the E. coli-expressed SCP, described here is terminated following the carboxy-terminal residue and, therefore, does not require autocatalysis. Nevertheless, the E., coli-expressed protein folds with the carboxy-terminal tryptophan residue, in the specificity pocket. Two crystallographically independent molecules, of SCP(106 to 266), which had two additional downstream residues and had, the essential S215 mutated to alanine, showed two distinct modes of, binding the uncleaved carboxy-terminal residues. These may represent, successive steps of binding substrate prior to catalytic cleavage., Refinement of the various crystal structures of SCP showed that the, amino-terminal arm from residues 107 to 113 was not disordered, but is, associated with neighboring molecules. Residues 108 to 111 bind into a, hydrophobic pocket composed primarily of Y180, W247 and F166. It had been, shown that the double mutant (Y180S; E183G), with the Y180S substitution, in this pocket, produced a large number of non-infectious virions, possibly because of modification in the interaction of the glycoprotein, spikes with core proteins. The crystal structure of this double mutant, showed that there was a large positional change in the side-chain of W247, which moved into the space created by the replacement of Y180 with serine., These conformational changes may alter the stability of the virion and, thus, regulate its functional requirements during cell entry.

==About this Structure==
1KXA is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Sindbis_virus Sindbis virus]. Known structural/functional Site: <scene name='pdbsite=TRI:Sindbis+Capsid+Protein+Has+The+Catalytic+Triad+Of+SER+Pr+...'>TRI</scene>. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KXA OCA]. 

==Reference==
Structural analysis of Sindbis virus capsid mutants involving assembly and catalysis., Choi HK, Lee S, Zhang YP, McKinney BR, Wengler G, Rossmann MG, Kuhn RJ, J Mol Biol. 1996 Sep 20;262(2):151-67. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=8831786 8831786]
[[Category: Sindbis virus]]
[[Category: Single protein]]
[[Category: Choi, H.K.]]
[[Category: Rossmann, M.G.]]
[[Category: chymotrypsin-like serine proteinase]]
[[Category: coat protein]]
[[Category: sindbis virus capsid protein]]
[[Category: wild type]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Feb  3 09:53:04 2008''