Molecular aspects of the high oxygen afinity of non-hypertensive hexa pegylated hemoglobin, [(SP-PEG5K)6-Hb]
Molecular aspects of the high oxygen afinity of non-hypertensive hexa pegylated hemoglobin, [(SP-PEG5K)6-Hb]
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DOI：
10.1080/10731190600974376
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发表时间：
2007-01-01
期刊：
影响因子：
--
通讯作者：
Acharya, A. Seetharama
中科院分区：
文献类型：
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作者：
Li, Dongxia;Manjula, Belur N.;Acharya, A. Seetharama
使用新设计的基于巯基化介导的马来酰亚胺化学的聚乙二醇化，六聚乙二醇化Hb（SP-PEG 5 K）（6）-Hb的开发已经验证了将“血浆体积膨胀剂”样性质工程化到Hb中和其血管活性的概念。六聚乙二醇化Hb的高O-2亲和力归因于其两个Cys-93（β）残基上的两条PEG-5 K链。在试图绘制HexaPEG化Hb的另外四个PEG-5 K链对O-2亲和力的影响的过程中，我们现在已经使用rHb（β C93 A）研究了单独表面氨基的PEG化对Hb的亚基界面相互作用和O-2亲和力的影响。PEG化rHb（β C93 A）的分子半径略小于（SP-PEG 5 K）（6）-Hb的分子半径，并且PEG化rHb（β C93 A）在Lys残基处的PEG化的总体位点选择性与（SP-PEG 5 K）（6）-Hb相当。质子NMR研究表明，蛋白质与PEG-5 K的缀合对其亚基界面相互作用没有任何显著影响。令人惊讶的是，PEG化对HbA和rHb（β C93 A）的O-2亲和力和玻尔效应的影响也几乎相同。显然，通过硫醇化介导的PEG化将PEG链缀合至Hb的Lys残基诱导Hb的水合壳（紧密结合的水分子层）的结构的独特变化，这进而诱导其R至T构象转变的约束以有利于更水合的R状态。
The development of hexaPEGylated Hb, (SP-PEG5K)(6)-Hb, using the newly designed thiolation-mediated maleimide chemistry based PEGylation, has validated the concept that engineering 'plasma volume expander' -like properties to Hb neutralizes its vasoactivity. The high O-2 affinity of hexaPEGylated Hb has been attributed to the two PEG-5K chains on its two Cys-93(beta) residues. In an attempt to map the influence of the additional four PEG-5K chains of HexaPEGylated Hb on the O-2 affinity, we have now investigated the influence of PEGylation of the surface amino groups alone on the subunit interface interactions and O-2 affinity of Hb using rHb(beta C93A). The molecular radius of PEGylated rHb(beta C93A) was slightly smaller than that of (SP-PEG5K)(6)-Hb, and the overall site-selectivity of PEGylation in the PEGylated rHb(beta C93A) at Lys-residues was comparable to that of (SP-PEG5K)(6)-Hb. Proton NMR studies have shown that the conjugation of the protein with PEG-5K does not have any significant influence on its subunit interface interactions. Surprisingly, the influence of PEGylation on the O-2 affinity and Bohr effect of HbA and rHb(beta C93A) is also nearly the same. Apparently, conjugation of PEG-chains to Lys residues of Hb by the thiolation mediated PEGylation induces unique changes in the structure of the hydration shell of Hb (layer of tightly bound water molecules), which, in turn, induces constraints in its R to T conformational transition to favor the more hydrated R-state.