Role of phenylalanine B10 in plant nonsymbiotic hemoglobins.
Role of phenylalanine B10 in plant nonsymbiotic hemoglobins.
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苯丙氨酸 B10 在植物非共生血红蛋白中的作用。
DOI：
10.1021/bi060716s
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Hargrove,MarkS
中科院分区：
文献类型：
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作者：
Smagghe,BenoitJ;Kundu,Suman;Hoy,JulieA;Halder,Puspita;Weiland,TheodoreR;Savage,Andrea;Venugopal,Anand;Goodman,Matthew;Premer,Scott;Hargrove,MarkS
所有植物都含有一类不寻常的血红蛋白，它们显示双组氨酰配位，但能够结合外源配体，如氧。结构同源的六配位血红蛋白（hxHbs）也存在于动物（脑珠蛋白和细胞珠蛋白）和一些蓝细菌中，它们被认为在自由基清除或配体传感中发挥作用。植物hxHbs可以从其他的区别，因为他们只是弱hexacocoordinate在亚铁态，但没有结构机制，调节hexacoordination已阐明解释这种行为。植物hxHbs在位置B10（PheB 10）处含有保守的Phe，其靠近可逆协调的远端HisE 7。我们研究了PheB 10突变对亚铁和三价铁氧化态六配位和外源配体结合的动力学和平衡常数的影响。六配位和配体结合的动力学和平衡常数沿着与CO-FTIR光谱，中点还原电位，以及两个关键突变蛋白（F40 W和F40 L）的晶体结构表明，PheB 10是一个重要的调节元件在六配位。我们表明，苯丙氨酸在这个位置是唯一的氨基酸，促进稳定的氧结合的亚铁血红蛋白和唯一的一个，促进配体结合在铁的氧化态。这项工作提出了一个结构机制，调节可逆的分子内协调植物hxHbs。
All plants contain an unusual class of hemoglobins that display bis-histidyl coordination yet are able to bind exogenous ligands such as oxygen. Structurally homologous hexacoordinate hemoglobins (hxHbs) are also found in animals (neuroglobin and cytoglobin) and some cyanobacteria, where they are thought to play a role in free radical scavenging or ligand sensing. The plant hxHbs can be distinguished from the others because they are only weakly hexcacoordinate in the ferrous state, yet no structural mechanism for regulating hexacoordination has been articulated to account for this behavior. Plant hxHbs contain a conserved Phe at position B10 (PheB10), which is near the reversibly coordinated distal HisE7. We have investigated the effects of PheB10mutation on kinetic and equilibrium constants for hexacoordination and exogenous ligand binding in the ferrous and ferric oxidation states. Kinetic and equilibrium constants for hexacoordination and ligand binding along with CO-FTIR spectroscopy, midpoint reduction potentials, and the crystal structures of two key mutant proteins (F40W and F40L) reveal that PheB10is an important regulatory element in hexacoordination. We show that Phe at this position is the only amino acid that facilitates stable oxygen binding to the ferrous Hb and the only one that promotes ligand binding in the ferric oxidation states. This work presents a structural mechanism for regulating reversible intramolecular coordination in plant hxHbs.