1a8f: Difference between revisions

The N-lobe of human serum transferrin (hTF/2N) has been expressed in baby, hamster kidney cells and crystallized in both orthorhombic (P212121) and, tetragonal (P41212) space groups. Both crystal forms diffract to high, resolution (1.6 and 1.8 A, respectively) and have been solved by molecular, replacement. Subsequent refinement resulted in final models for the, structure of hTF/2N that had crystallographic R-factors of 18.1 and 19.7%, for the two crystal forms, respectively; these models represent the, highest-resolution transferrin structures determined to date. The hTF/2N, polypeptide has a folding pattern similar to those of other transferrins, including the presence of a deep cleft that contains the metal-binding, site. In contrast to other transferrins, both crystal forms of hTF/2N, display disorder at the iron-binding site; model building suggests that, this disorder consists of alternative conformations of the synergistically, bound carbonate anion, the side chain for Arg-124, and several solvent, molecules. Subsequent refinement revealed that conformation A has an, occupancy of 0.63-0. 65 and corresponds to the structure of the, iron-binding site found in other transferrins. The alternative, conformation B has an occupancy of 0.35-0.37; in this structure, the, carbonate has rotated 30 degrees relative to the iron and the side chain, for Arg-124 has moved to accommodate the new carbonate position. Several, water molecules appear to stabilize the carbonate anion in the two, conformations. These structures are consistent with the protonation of the, carbonate and resulting partial removal of the anion from the metal; these, events would occur prior to cleft opening and metal release.

1A8F is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with CO3 and FE as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Site: FE. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1A8F OCA].  

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