Detection of threonine structural changes upon formation of the M-intermediate of bacteriorhodopsin: evidence for assignment to Thr-89.
Detection of threonine structural changes upon formation of the M-intermediate of bacteriorhodopsin: evidence for assignment to Thr-89.
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细菌视紫红质 M-中间体形成时苏氨酸结构变化的检测：分配给 Thr-89 的证据。
DOI：
10.1016/s0005-2728(98)00088-7
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Rothschild,KJ
中科院分区：
文献类型：
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作者：
Liu,X;Lee,MJ;Coleman,M;Rath,P;Nilsson,A;Fischer,WB;Bizounok,M;Herzfeld,J;Karstens,WF;Raap,J;Lugtenburg,J;Rothschild,KJ
用傅里叶变换红外差光谱法研究了苏氨酸残基在细菌视紫红质（bR）光循环中的行为。用~（18）O标记的l-苏氨酸（l-[3- 18 O]threonine）掺入bR中，测定了bR→M的FTIR差谱。根据~（18）O引起的同位素频移和简正模计算，将谱带归属于苏氨酸振动模。在3500 cm-1区域，一条负带被指定为苏氨酸的OH延伸。在1125 cm-1区域，一个负带被分配给一个混合的CH 3rock/CO伸缩模。这两个带的频率表明在光适应bR中存在至少一个氢键合的苏氨酸羟基，其通过形成M中间体而经历结构变化。由Thr-89→Asn取代而非Thr-46→Asn或Asp-96→Asn取代诱导的光谱变化与这些条带归属于Thr-89一致。这些结果沿着另一个有关突变体Thr-89→Asn的研究表明，bR的活性位点包括Thr-89，它与亚视黄基Schiff碱和Asp-85的相互作用可能在调节细菌视紫红质的颜色和质子向Schiff碱的转移中起重要作用。
The behavior of threonine residues in the bacteriorhodopsin (bR) photocycle has been investigated by Fourier transform infrared difference spectroscopy. l-Threonine labeled at the hydroxyl group with18O (l-[3-18O]threonine) was incorporated into bR and the bR→M FTIR difference spectra measured. Bands are assigned to threonine vibrational modes on the basis of18O induced isotope frequency shifts and normal mode calculations. In the 3500 cm−1region, a negative band is assigned to the OH stretch of threonine. In the 1125 cm−1region, a negative band is assigned to a mixed CH3rock/CO stretch mode. The frequency of both these bands indicates the presence of at least one hydrogen bonded threonine hydroxyl group in light adapted bR which undergoes a change in structure by formation of the M intermediate. Spectral changes induced by the substitution Thr-89→Asn but not Thr-46→Asn or Asp-96→Asn are consistent with the assignment of these bands to Thr-89. These results along with another related study on the mutant Thr-89→Asn indicate that the active site of bR includes Thr-89 and that its interaction with the retinylidene Schiff base and Asp-85 may play an important role in regulating the color of bacteriorhodopsin and the transfer of a proton to the Schiff base.