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| {{STRUCTURE_1g7a| PDB=1g7a | SCENE= }} | | {{STRUCTURE_1g7a| PDB=1g7a | SCENE= }} |
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| '''1.2 A structure of T3R3 human insulin at 100 K'''
| | ===1.2 A structure of T3R3 human insulin at 100 K=== |
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| ==Overview==
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| The structure of T(3)R(3) hexameric human insulin has been determined at 100 K from two different crystals at 1.2 and 1.3 A resolution and refined to residuals of 0.169 and 0.176, respectively. Owing to a phase change, the c axis is double its room-temperature value and the asymmetric unit contains two independent TR(f) insulin dimers. Compared with the orientation in the room-temperature structure, one dimer undergoes a rotation about the c axis of -5 degrees, while the second is rotated +4 degrees. A superposition of the backbone atoms of the two independent dimers shows that the C(alpha) atoms of five residues within the R(f)-state monomers are displaced by more than 1.0 A; smaller displacements are observed for the T-state monomers. Four zinc ions lie on the crystallographic threefold axis and each forms bonds to three symmetry-related HisB10 N(varepsilon2) atoms from the T- and R(f)-state trimers. While three of the zinc ions are tetrahedrally coordinated with a chloride ion completing the coordination sphere, mixed tetrahedral/octahedral coordination is observed for one of the T-state zinc ions. The three symmetry-related "phenolic binding sites" in one hexamer contain water molecules and a glycerol molecule, but the same sites in the second hexamer are occupied by a zinc ion coordinated to an alternate conformation of HisB10, a symmetry-related HisB5 and two chloride ions. Two additional and partially occupied zinc ion sites are observed at the interface between the two independent dimers. One zinc ion is coordinated by a T-state HisB5 of one dimer, an R-state HisB5 of the second dimer and two water molecules; the second zinc ion is coordinated by an alternate side-chain conformation of the T-state HisB5 and three water molecules. The carboxyl group of one GluB13 side chain, which exists in two discrete conformations, appears to be protonated, because short contacts exist to a second carboxyl group or to a carbonyl O atom. | | The line below this paragraph, {{ABSTRACT_PUBMED_11468392}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11468392 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11468392}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Smith, G D.]] | | [[Category: Smith, G D.]] |
| [[Category: T3r3 insulin hexamer]] | | [[Category: T3r3 insulin hexamer]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 17:13:51 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 04:49:18 2008'' |