1n73: Difference between revisions

[[Image:1n73.gif|left|200px]]<br /><applet load="1n73" size="350" color="white" frame="true" align="right" spinBox="true"  

The crystal structure of fragment double-D from factor XIII-cross-linked lamprey fibrin has been determined at 2.9 A resolution. The 180 kDa covalent dimer was cocrystallized with the peptide Gly-His-Arg-Pro-amide, which in many fibrinogens, but not that of lamprey, corresponds to the B-knob exposed by thrombin. The structure was determined by molecular replacement, a recently determined structure of lamprey fragment D being used as a search model. GHRPam was found in both the gamma- and beta-chain holes. Unlike the situation with fragment D, the crystal packing of the cross-linked double-D structure exhibits two different D-D interfaces, each gamma-chain facing gamma-chains on two other molecules. One of these (interface I) involves the asymmetric interface observed in all other D fragments and related structures. The other (interface II) encompasses a completely different set of residues. The two abutments differ in that interface I results in an "in line" arrangement of abutting molecules and the interface II in a "zigzag" arrangement. So far as can be determined (the electron density could only be traced on one side of the cross-links), it is the gamma-chains of the newly observed zigzag units (interface II) that are joined by the reciprocal epsilon-amino-gamma-glutamyl cross-links. Auspiciously, the same novel D-D interface was observed in two lower-resolution crystal structures of human double-D preparations that had been crystallized under unusual circumstances. These observations show that double-D structures are linked in a way that is sufficiently flexible to accommodate different D-D interfaces under different circumstances.

1N73 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Petromyzon_marinus Petromyzon marinus] with <scene name='pdbligand=NAG:'>NAG</scene> and <scene name='pdbligand=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1N73 OCA].  

[[Category: Doolittle, R F.]]

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