High-resolution crystallographic analysis of a co-operative dimeric hemoglobin.
High-resolution crystallographic analysis of a co-operative dimeric hemoglobin.
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DOI：
10.1006/jmbi.1994.1019
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发表时间：
1994-01
影响因子：
5.6
通讯作者：
W. Royer
中科院分区：
文献类型：
--
作者：
W. Royer
高分辨率晶体结构的合作二聚血红蛋白从血蛤Scapharca inaequivalvis已被确定在unliganded（脱氧）和一氧化碳（CO）配位状态。脱氧结构已在1.6 A分辨率下细化至R因子0.158，CO结构已在1.4 A分辨率下细化至R因子0.159。这些结构揭示了参与合作的配体结合，只涉及一个小的旋转的亚基，但非常引人注目的三级变化的接口的结构转变的细节。F-螺旋中的少量残基似乎介导了这种简单血红蛋白的协同性。每个亚基的氧亲和力似乎在很大程度上取决于苯丙氨酸97，其侧链包在血红素口袋中的脱氧状态，但在CO-配体结构的界面被挤出的处置。配体结合血红素组的直接参与是一个新的功能的亚基接口，并出现重要的亚基间通信。连接改变了构象的血红素丙酸酯基团沿着与两个相互作用的残基从血红素相关的亚基。这两个残基，赖氨酸96和天冬酰胺100，以影响该亚基的配体亲和力的方式将一个亚基的血红素与第二个亚基的F-螺旋连接。界面高度水合有序的水分子，这可能是重要的两个结构的稳定。
High-resolution crystal structures of the co-operative dimeric hemoglobin from the blood clam Scapharca inaequivalvis have been determined in the unliganded (deoxy) and carbon monoxide (CO) liganded states. The deoxy structure has been refined at 1.6 A resolution to an R-factor of 0.158 and the CO structure has been refined at 1.4 A resolution to an R-factor of 0.159. These structures reveal details of the structural transitions involved in co-operative ligand binding that involve only a minor rotation of subunits but very striking tertiary changes at the interface. A small number of residues in the F-helix appear to mediate co-operativity in this simple hemoglobin. The oxygen affinity of each subunit appears to be largely dictated by the disposition of phenylalanine 97, whose side-chain packs in the heme pocket in the deoxy state but is extruded towards the interface in the CO-liganded structure. Direct involvement of the ligand-binding heme group is a novel feature of the subunit interface and appears important for intersubunit communication. Ligation alters the conformation of the heme propionate groups along with two interacting residues from the symmetry-related subunit. These two residues, lysine 96 and asparagine 100, link the heme of one subunit with the F-helix of the second subunit in such a way as to influence the ligand affinity of that subunit. The interface is highly hydrated by well-ordered water molecules that are likely to be important in the stabilization of the two structures.