1pma: Difference between revisions

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

The three-dimensional structure of the proteasome from the archaebacterium Thermoplasma acidophilum has been elucidated by x-ray crystallographic analysis by means of isomorphous replacement and cyclic averaging. The atomic model was built and refined to a crystallographic R factor of 22.1 percent. The 673-kilodalton protease complex consists of 14 copies of two different subunits, alpha and beta, forming a barrel-shaped structure of four stacked rings. The two inner rings consist of seven beta subunits each, and the two outer rings consist of seven alpha subunits each. A narrow channel controls access to the three inner compartments. The alpha 7 beta 7 beta 7 alpha 7 subunit assembly has 72-point group symmetry. The structures of the alpha and beta subunits are similar, consisting of a core of two antiparallel beta sheets that is flanked by alpha helices on both sides. The binding of a peptide aldehyde inhibitor marks the active site in the central cavity at the amino termini of the beta subunits and suggests a novel proteolytic mechanism.

1PMA is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Thermoplasma_acidophilum Thermoplasma acidophilum]. Active as [http://en.wikipedia.org/wiki/Proteasome_endopeptidase_complex Proteasome endopeptidase complex], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.25.1 3.4.25.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1PMA OCA].  

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