细菌内毒素对人的交联和天然血红蛋白的影响。,Biochemistry

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细菌内毒素对人的交联和天然血红蛋白的影响。
Biochemistry ( IF 2.9 ) Pub Date : 1995 Sep 5
Kaca, W, Roth, R I, Vandegriff, K D, Chen, G C, Kuypers, F A, Winslow, R M, Levin, J

先前的研究表明，血红蛋白（Hb）是细菌内毒素（脂多糖，LPS）的结合蛋白，并且在Hb存在时LPS的结构和生物学活性会发生改变。在本研究中，通过分析200-650 nm波长范围内Hb的吸收光谱和圆二色性光谱，研究了LPS对天然人HbA0和共价交联Hb（alpha alpha Hb）结构的影响。将oxyHb与几种LPS一起孵育会导致414 nm处的主要Soret带强度降低，最大峰移至410 nm，541和577 nm处的主要可见区峰强度降低，在630 nm范围内可见光吸收增加。所得光谱是高铁血红蛋白形成的特征。这些光谱变化与时间有关，与LPS浓度有关。高铁血红蛋白的产生在化学修饰的，部分脱乙酰化的粗糙脂多糖中尤为突出，在天然，完整的粗糙脂多糖和天然光滑脂多糖中均观察到较少的程度。还直接测试了LPS对高铁血红蛋白吸收光谱的影响。在LPS存在下，高铁血红蛋白向半色素的转化得到了证明，并且证明是可逆的。Hb的圆二色性光谱分析表明，LPS诱导的可见光区和Soret区的光谱变化与大量metHb的产生相一致，但在远紫外区（210-240 nm）未显示出任何变化。而且，与几种LPS孵育后，Hb氧亲和力仅略有改变。总之，吸收光谱和圆二向色光谱的分析表明，LPS可能产生易于氧化的alpha alpha交联的人Hb和天然人HbA0，而在珠蛋白的二级结构中却没有实质性改变。

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Effects of bacterial endotoxin on human cross-linked and native hemoglobins.

Previous investigations have demonstrated that hemoglobin (Hb) is a binding protein for bacterial endotoxin (lipopolysaccharide, LPS) and that the structure and biological activity of LPS are altered in the presence of Hb. In the present study, the influence of LPS on the structure of native human HbA0 and covalently cross-linked Hb (alpha alpha Hb) was studied by analyzing the absorption and circular dichroic spectra of Hb in the wavelength region of 200-650 nm. Incubation of oxyHb with each of several LPSs resulted in a decrease in the intensity of the major Soret band at 414 nm with a shift in the maximum peak to 410 nm, decreases in the intensities of the major visible region peaks at 541 and 577 nm, and the appearance of increased absorbance in the visible region in the range of 630 nm. The resultant spectra are characteristic of methemoglobin formation. These spectral changes were time-dependent and LPS-concentration-dependent. Production of methemoglobin was prominent with chemically modified, partially deacetylated rough LPS, and was observed to a lesser extent both with native, complete rough and with native smooth LPSs. The influence of LPS on the absorption spectrum of methemoglobin also was directly tested. The conversion of methemoglobin to hemichrome in the presence of LPS was demonstrated and was shown to be reversible. Analysis of circular dichroic spectra of Hb demonstrated LPS-induced spectral changes in the visible and Soret regions consistent with the production of a substantial quantity of metHb, but did not demonstrate any alteration in the far-UV region (210-240 nm). Moreover, Hb oxygen affinity was only slightly altered after incubation with any of several LPSs. In conclusion, analyses of absorption and circular dichroic spectra reveal the potential of LPS to produce a facilitated oxidation of both alpha alpha-cross-linked human Hb and native human HbA0, without substantial changes in the secondary structure of the globin.

更新日期：2017-01-31

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