Titration behavior and tautomeric states of individual histidine residues of myoglobins. Application of natural abundance carbon 13 nuclear magnetic resonance spectroscopy.
Titration behavior and tautomeric states of individual histidine residues of myoglobins. Application of natural abundance carbon 13 nuclear magnetic resonance spectroscopy.
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肌红蛋白的各个组氨酸残基的滴定行为和互变异构状态。
DOI：
10.1016/s0021-9258(17)40147-5
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发表时间：
1977
期刊：
影响因子：
--
通讯作者：
A. Allerhand
中科院分区：
文献类型：
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作者：
D. J. Wilbur;A. Allerhand
通过观察马铁肌红蛋白、马氰铁肌红蛋白和红袋鼠氰铁肌红蛋白天然丰度13 C傅里叶变换NMR谱（15.18 MHz和37”）中非质子化芳香碳共振化学位移的pH依赖性，研究了肌红蛋白中单个组氨酸残基的滴定行为。在氰铁肌红蛋白的情况下，芳香族氨基酸残基的所有非质子化侧链碳产生可检测的共振，但在马铁肌红蛋白的情况下，这种类型的28个碳中只有24个产生可检测的共振。马氰铁肌红蛋白的11个组氨酸残基中有8个（袋鼠蛋白的10个组氨酸中有7个）表现出滴定行为（pK值在4.4至6.6范围内）。每种滴定组氨酸的咪唑形式主要（或完全）处于NfZ-H互变异构状态。两个滴定共振的cyanofriermyoglobins（与pK值为5.3和约4.5）不产生可检测的信号，在光谱的马ferrymyoglobin。这两个共振被分配给His-64和His-97的0 '（不是一对一的）。马铁肌红蛋白的六个滴定共振中的五个具有pK值（5.5、5.7、6.5、6.6和6.6），这与从质子NMR光谱获得的六个报告的pK值中的五个一致。在我们的马铁肌红蛋白和氰基铁肌红蛋白的13 C NMR谱中观察到的第六个pK（< 5）在报道的质子NMR数据中没有检测到对应物。此外，“高”pK（约7.4至8.0）的铁肌红蛋白的质子NMR研究报告中没有对应的在我们的13 C NMR谱的马铁肌红蛋白和cyanoferrymyoglobins从马，袋鼠，抹香鲸。三个nontitrating组氨酸CY共振的cyanoferrymyoglobins从马和袋鼠（没有观察到马铁肌红蛋白的光谱）被分配到协调的His-93。我们的研究结果表明，两个未配位的非滴定组氨酸残基是在咪唑或在NS 1-H咪唑状态（或两种状态的混合物）。肌红蛋白的晶体结构表明它们是His-24和His-36。我们还确定了两个色氨酸的CY，C62和@的共振
The titration behavior of individual histidine residues of myoglobins has been studied by observing the pH dependence of the chemical shifts of the nonprotonated aromatic carbon resonances in natural abundance 13C Fourier transform NMR spectra (at 15.18 MHz and 37”), of horse ferrimyoglobin, horse cyanoferrimyoglobin, and red kangaroo cyanoferrimyoglobin. In the case of the cyanoferrimyoglobins, all nonprotonated side chain carbons of aromatic amino acid residues yield detectable resonances, but only 24 of the 28 carbons of this type yield detectable resonances in the case of horse ferrimyoglobin. Eight of the 11 histidine residues of horse cyanoferrimyoglobin(and 7 of the 10 histidines of the kangaroo protein) exhibit titration behavior (pK values in the range 4.4 to 6.6). The imidazole form of each titrating histidine is predominantly(or entirely) in the NfZ-H tautomeric state. Two of the titrating resonances of the cyanoferrimyoglobins(with pK values of 5.3 and about 4.5) do not yield detectable signals in spectra of horse ferrimyoglobin. These two resonances are assigned to 0’of His-64 and His-97 (not on a one-to-one basis). Five of the six titrating resonances of horse ferrimyoglobin have pK values (5.5, 5.7, 6.5, 6.6, and 6.6) which are consistent with those of five of the six reported pK values that were obtained from proton NMR spectra. The sixth pK (< 5), observed in our 13C NMR spectra of horse ferrimyoglobin and the cyanoferrimyoglobins, does not have a detected counterpart in the reported proton NMR data. Also, the “high” pK (about 7.4 to 8.0) reported in the proton NMR studies of ferrimyoglobins has no counterpart in our 13C NMR spectra of horse ferrimyoglobin and the cyanoferrimyoglobins from horse, kangaroo, and sperm whale.One of the three nontitrating histidine CY resonances of the cyanoferrimyoglobins from horse and kangaroo (not observed in spectra of horse ferrimyoglobin) is assigned to the coordinated His-93. Our results indicate that the two uncoordinated nontitrating histidine residues are either in the imidazolium or in the NSl-H imidazole state (or a mixture of the two states). The crystal structure of myoglobin suggests that these are His-24 and His-36. We also identify the resonances of CY, C62, and@ of the two tryptophan