Spectroscopic study of Ser92 mutants of human myoglobin: hydrogen bonding effect of Ser92 to proximal His93 on structure and property of myoglobin.
Spectroscopic study of Ser92 mutants of human myoglobin: hydrogen bonding effect of Ser92 to proximal His93 on structure and property of myoglobin.
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人肌红蛋白 Ser92 突变体的光谱研究：Ser92 与近端 His93 的氢键作用对肌红蛋白结构和性质的影响。
作者：
Y. Shiro;T. Iizuka;K. Marubayashi;T. Ogura;T. Kitagawa;S. Balasubramanian;S. Boxer
中子衍射研究已经证明，Ser 92（F7）的羟基氧与肌红蛋白（Mb）中的近端His 93（48）N-OH质子氢键合[Cheng，X.，& Shoenborn，B. P.（1991）J. Mol. 220，381-399]。为了研究这种氢键的重要性，在人Mb中，Ser 92被Ala和Asp取代。通过比较Mb（S92 A）在几种自旋和氧化态下与野生型Mb的光学、1H-NMR、共振拉曼和红外光谱，发现突变引起血红素近端侧的结构变化，但在远端侧不引起结构变化。Mb（S92 A）和Mb（WT）的氰脲酸形式的NMR光谱的比较表明，在His 93和Ser 92之间的氢键丧失后，His 93的咪唑平面围绕Fe-N δ（His 93）键稍微旋转。CO复合物的2D 1H-NMR测量表明，Ser 92突变为Ala改变了His 97咪唑基团与血红素平面的相对位置，但这种变化并不像猪Mb的Ser 92突变体的晶体数据中报道的那么剧烈[Smerdon等人。（1993）Biochemistry 32，5132-5138]。另一方面，配体（CO，O2）结合仅受此突变的轻微影响。从这些结果中，我们得出结论，Ser 92-His 93氢键保持近端血红素口袋的蛋白质结构，但它不会强烈影响血红素以及His 93咪唑环的电子结构。（250字处删节）
Neutron diffraction studies have demonstrated that the hydroxyl group oxygen of Ser92(F7) is hydrogen bonded to the proximal His93(48) N epsilon H proton in myoglobin (Mb) [Cheng, X., & Shoenborn, B. P. (1991) J. Mol. Biol. 220, 381-399]. In order to examine the importance of this hydrogen bond, Ser92 was replaced with Ala and Asp in human Mb. By comparing the optical, 1H-NMR, resonance Raman, and IR spectra of Mb(S92A) in several spin and oxidation states with those of wild-type Mb, it was found that the mutation causes a structural change on the heme proximal side but not on the distal side. Comparison of the NMR spectra of the cyanomet form of Mb(S92A) and Mb(WT) suggests that the imidazole plane of His93 rotates somewhat around the Fe-N delta (His93) bond upon loss of the hydrogen bond between His93 and Ser92. The 2D 1H-NMR measurements of the CO complexes show that mutation of Ser92 to Ala changes the relative position of the His97 imidazole group to the heme plane, but the change is not so drastic as reported in the crystal data of Ser92 mutant of pig Mb [Smerdon et al. (1993) Biochemistry 32, 5132-5138]. On the other hand, ligand (CO, O2) binding is only slightly affected by this mutation. From these results, we conclude that the Ser92-His93 hydrogen bond maintains the protein structure of the proximal heme pocket, but it does not strongly affect the electronic structure of the heme as well as of the His93 imidazole ring.(ABSTRACT TRUNCATED AT 250 WORDS)
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