1qoi: Difference between revisions

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

The cyclophilin SnuCyp-20 is a specific component of the human U4/U6 small nuclear ribonucleoprotein particle involved in the nuclear splicing of pre-mRNA. It stably associates with the U4/U6-60kD and -90kD proteins, the human orthologues of the Saccharomyces cerevisiae Prp4 and Prp3 splicing factors. We have determined the crystal structure of SnuCyp-20 at 2.0-A resolution by molecular replacement. The structure of SnuCyp-20 closely resembles that of human cyclophilin A (hCypA). In particular, the catalytic centers of SnuCyp-20 and hCypA superimpose perfectly, which is reflected by the observed peptidyl-prolyl-cis/trans-isomerase activity of SnuCyp-20. The surface properties of both proteins, however, differ significantly. Apart from seven additional amino-terminal residues, the insertion of five amino acids in the loop alpha1-beta3 and of one amino acid in the loop alpha2-beta8 changes the conformations of both loops. The enlarged loop alpha1-beta3 is involved in the formation of a wide cleft with predominantly hydrophobic character. We propose that this enlarged loop is required for the interaction with the U4/U6-60kD protein.

1QOI is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1QOI OCA].  

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