Solution structure determination of the heme cavity in the E7 His-->Val cyano-met myoglobin point mutant based on the 1H NMR detected dipolar field of the iron: evidence for contraction of the heme pocket.
Solution structure determination of the heme cavity in the E7 His-->Val cyano-met myoglobin point mutant based on the 1H NMR detected dipolar field of the iron: evidence for contraction of the heme pocket.
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基于 1H NMR 检测到的铁偶极场，确定 E7 His-->Val 氰基-met 肌红蛋白点突变体中血红素腔的溶液结构：血红素袋收缩的证据。
DOI：
10.1021/bi00072a024
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
Sligar,SG
中科院分区：
文献类型：
--
作者：
Rajarathnam,K;Qin,J;LaMar,GN;Chiu,ML;Sligar,SG
1993年3月23日收到的修订稿摘要：用2D方法分析了抹香鲸His[E7]Val肌红蛋白(Mb)点突变的氰化物复合体的核磁共振谱，得到了活性部位残基的归属，包括被取代的Val E7。偶极移位的近端残基被用来定量地定位分子骨架中顺磁极化率张量的磁轴。与配体倾斜相关的长轴的取向与血红素正常的方向约为15，如野生型(WT)Mb中所发现的那样，但相对于WT以~40向血红素-中位位置旋转的方向倾斜，与His[E7]Gly突变体[Rajarathnam，K.，La Mar，G.N.，Chiu，M.，&Sliar，S.G.(1992)J.Am]中的方向类似化学。SoC。114,9048-9058]，Fe+3-CN单元倾角不变的变化方向与MbCO[Kuriyan，J.，Wilz，S.，Karplus，M.，&Petsko，G.A.(1986)J.Mol]的势能面的计算定性地一致。比奥尔。192,133-154]，结果表明，他的E7对配体的倾斜没有显著的贡献，但强烈地影响了配体的倾斜方向。分别分析了E-螺旋和血红素1，8-甲基之间观测和预测的E-螺旋主干质子的偶极位移和它们各自的核Overhauser效应的扰动模式之间的偏差，并同意E-螺旋沿铁的方向平移约0.8A。Phe CD1的观测到的偶极位移与预测的偶极位移之间的差异表明，平行于血红素的环向E螺旋移动了~0.5°。E-螺旋和Phe-CD1的运动与眼袋的收缩一致，以填补His Val替换所创造的空间。观察到的取代Val E7侧链的偶极位移与E-螺旋移动和不移动时计算的偶极位移之间的相关性证实了E-螺旋的移动，并允许定量描述Val的取向。结论是，顺磁磁化率张量的偶极场为确定肌红蛋白和血红蛋白远端点突变的色素复合体中的血红素空腔结构提供了重要的定量约束。肌红蛋白是局部结构控制蛋白质功能的典型例子(Stryer，1988)。远端组氨酸(E7)是肌红蛋白(MBS)1和血红蛋白(HBS)之间高度保守的残基，被认为在配体结合的各个方面都起着关键作用。有人认为，MBS和HBS已经进化到选择性地结合02(图IB)而不是CO(图1A)，这种选择性被归因于远端组氨酸通过氢键稳定02的结合，并通过将CO从线性位置倾斜来破坏CO的结合的能力(即，图1C，D)(Phillips，1980；Coliman等人，1976)。氰化铁的络合物Fe3+-CN与Fe2+-CO是同位异构体
Revised Manuscript Received March 23, 1993 abstract: The NMR spectrum of the cyanomet complex of the sperm whale His [E7] Val myoglobin (Mb) point mutant has been analyzedby 2D methods to yield the assignments for the active site residues, including the substituted Val E7. The dipolar shifted proximal residues are used to quantitatively locate the magnetic axes for the paramagnetic susceptibility tensor in the molecular framework. The orientation of the major axis, which correlates with the ligand tilt, is~15 from theheme normal, as found in wild-type (WT) Mb, but is tilted in a direction rotated~ 40 toward theheme-meso position with respect to WT and similar to that in the His [E7] Gly mutant [Rajarathnam, K., La Mar, G. N., Chiu, M., & Sligar, S. G.(1992) J. Am. Chem. Soc. 114, 9048-9058], The altered direction of an unchanged tilt angle for the Fe+ 3-CN unit is shown to be qualitatively consistent with earliercomputations of the potential energy surface for MbCO [Kuriyan, J., Wilz, S., Karplus, M., & Petsko, G. A.(1986) J. Mol. Biol. 192,133-154], It is concluded that His E7 does not significantly contribute to the ligand tilt but strongly influences the direction oftilt. Deviations betweenobserved and predicteddipolar shifts for the E-helix backbone protons and perturbed patterns of their respective nuclear Overhauser effect between the E-helix and the heme 1, 8-methyls are separately analyzed for movement of the E-helix and agree on a translation of the E-helix of the order of 0.8 A in a direction toward the iron. The discrepancybetween observed and predicteddipolar shifts for Phe CD1 indicates a~ 0.5-Á movement by the ring parallel to the heme and towards the E-helix. The E-helix and Phe CD 1 movements are consistent with a contraction of the pocket to fill the space created by the His Val substitution. The correlation between the observed dipolar shifts of the substituted Val E7 side chain and those calculated as a function of rotation of theresidue with and without movement of the E-helixconfirm themovement of the E-helix and allow a quantitative description of the Val orientation. It is concluded that the dipolar fieldof the paramagnetic susceptibility tensor provides an important quantitative constraint for defining the heme cavity structure in cyanomet complexes of distal point mutants of myoglobin and hemoglobin.Myoglobin serves as a textbook example for the control of protein function by local structure (Stryer, 1988). The distal histidine (E7) is a highly conserved residue among the myoglobins (Mbs) 1 and hemoglobins (Hbs) and is thought to play a key role in all aspects of ligandbinding. It has been argued that Mbs and Hbs have evolved to selectively bind02 (Figure IB) in preference to CO (Figure 1A), and this selectivity has been attributed to the ability of the distal histidine to stabilize binding of 02 by hydrogen bonding and destabilize binding of CO by tilting it from a linear position (ie, Figure 1C, D)(Phillips, 1980; Coliman et al., 1976). The ferric cyanide complex, Fe3+-CN, is isosteric with Fe2+-CO
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影响因子：
5.6
作者：
W. Steigemann;E. Weber
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DOI：
--
发表时间：
1973
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Biochimica et Biophysica Acta
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影响因子：
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作者：
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DOI：
--
发表时间：
1992
期刊：
影响因子：
--
作者：
K. Rajarathnam;G. N. Mar;M. Chiu;S. Sligar
通讯作者：
S. Sligar
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影响因子：
5.6
作者：
Dalvit,C;Wright,PE
通讯作者：
Wright,PE