Azide and Acetate Complexes Plus Two Iron-depleted Crystal Structures of the Di-iron Enzyme Δ9 Stearoyl-Acyl Carrier Protein Desaturase
Azide and Acetate Complexes Plus Two Iron-depleted Crystal Structures of the Di-iron Enzyme Δ9 Stearoyl-Acyl Carrier Protein Desaturase
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叠氮化物和乙酸盐复合物加上二铁酶 α9 硬脂酰酰基载体蛋白去饱和酶的两种贫铁晶体结构
DOI：
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发表时间：
2003
影响因子：
4.8
通讯作者：
Y. Lindqvist
中科院分区：
文献类型：
--
作者：
M. Moche;J. Shanklin;A. Ghoshal;Y. Lindqvist
Δ9硬脂酰-酰基载体蛋白（ACP）去饱和酶是一种μ-氧桥双铁酶，属于I类大螺旋束蛋白，催化NADPH和O2依赖性形成硬脂酰-ACP中的顺式双键。测定了蓖麻Δ9硬脂酰-ACP去饱和酶的叠氮化物和乙酸盐复合物的晶体结构，以及脱铁和单铁形式。在叠氮配合物中，配体在活性中心的两个铁离子之间形成μ-1，3-桥，取代松散结合的水分子。乙酸盐络合物的结构是类似的，其中乙酸盐以相对于二铁中心相同的取向桥接二铁中心。然而，在该复合物中，铁配体Glu 196已经将其配位模式从双齿改变为单齿，这是在Δ9硬脂酰-ACP去饱和酶中首次观察到羧酸移位的晶体学观察。这两种配合物被提出来模拟在催化周转期间存在的μ-1，2过氧中间体。在Δ9硬脂酰-ACP去饱和酶-叠氮化物复合物和还原的赤藓红蛋白-叠氮化物复合物中的二铁中心之间存在惊人的结构相似性。这表明Δ9硬脂酰-ACP去饱和酶可能以低速率催化外源性过氧化氢形成水。从铁中心结构的相似性，我们提出氧化去饱和酶中的μ-氧代桥与二铁中心结合，如在红菊酯中，而不是如报道的核糖核苷酸还原酶的R2亚基和甲烷单加氧酶的羟化酶亚基。一铁耗尽的去饱和酶物种的晶体结构表明，对包含二铁中心的两个铁离子的亲和力是不相等的，Fe 1是较高亲和力位点，Fe 2是较低亲和力位点。
Δ9 stearoyl-acyl carrier protein (ACP) desaturase is a μ-oxo-bridged di-iron enzyme, which belongs to the structural class I of large helix bundle proteins and that catalyzes the NADPH and O2-dependent formation of a cis-double bond in stearoyl-ACP. The crystal structures of complexes with azide and acetate, respectively, as well as the apoand single-iron forms of Δ9 stearoyl-ACP desaturase from Ricinus communis have been determined. In the azide complex, the ligand forms a μ-1,3-bridge between the two iron ions in the active site, replacing a loosely bound water molecule. The structure of the acetate complex is similar, with acetate bridging the di-iron center in the same orientation with respect to the di-iron center. However, in this complex, the iron ligand Glu196 has changed its coordination mode from bidentate to monodentate, the first crystallographic observation of a carboxylate shift in Δ9 stearoyl-ACP desaturase. The two complexes are proposed to mimic a μ-1,2 peroxo intermediate present during catalytic turnover. There are striking structural similarities between the di-iron center in the Δ9 stearoyl-ACP desaturase-azide complex and in the reduced rubrerythrin-azide complex. This suggests that Δ9 stearoyl-ACP desaturase might catalyze the formation of water from exogenous hydrogen peroxide at a low rate. From the similarity in iron center structure, we propose that the μ-oxo-bridge in oxidized desaturase is bound to the di-iron center as in rubrerythrin and not as reported for the R2 subunit of ribonucleotide reductase and the hydroxylase subunit of methane monooxygenase. The crystal structure of the one-iron depleted desaturase species demonstrates that the affinities for the two iron ions comprising the di-iron center are not equivalent, Fe1 being the higher affinity site and Fe2 being the lower affinity site.
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DOI：
10.1073/pnas.90.6.2486
发表时间：
1993-03-15
影响因子：
11.1
作者：
FOX, BG;SHANKLIN, J;MUNCK, E
通讯作者：
MUNCK, E
影响因子：
15
作者：
D. Whittington;S. Lippard
通讯作者：
D. Whittington;S. Lippard
影响因子：
2.9
作者：
C. Rogge;B. Fox
通讯作者：
C. Rogge;B. Fox
影响因子：
2.9
作者：
Broadwater, JA;Ai, JY;Fox, BG
通讯作者：
Fox, BG
影响因子：
2.9
作者：
FOX, BG;SHANKLIN, J;SANDERSLOEHR, J
通讯作者：
SANDERSLOEHR, J