Infrequent cavity-forming fluctuations in HPr from Staphylococcus carnosus revealed by pressure- and temperature-dependent tyrosine ring flips
Infrequent cavity-forming fluctuations in HPr from Staphylococcus carnosus revealed by pressure- and temperature-dependent tyrosine ring flips
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DOI：
10.1110/ps.04877104
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发表时间：
2004-12-01
期刊：
影响因子：
8
通讯作者：
Kalbitzer, HR
中科院分区：
文献类型：
--
作者：
Hattori, M;Li, H;Kalbitzer, HR
球状蛋白质的罕见结构波动很少被检测和详细研究。利用在线细胞高压核磁共振技术，在3 ~ 200 MPa压力和257 ~ 313 K温度范围内，研究了肉色葡萄球菌（Staphylococcus carnosus）HPr的一个酪氨酸环发生非常缓慢的环翻转过程. Tyr 6的环被埋在P-片层和α-螺旋之间（水可及面积小于0.26 mm（2）），其羟基质子参与内部氢键。根据Tyr 6的H-δ 1、H-δ 2和H-ε 1、H-ε 2的线形分析，确定了类似于10（5）s（-1）的环翻转速率10（1），给出了活化体积Δ V 0.044 +/- 0.008 nm（双刃）（3）（27 mL mol（-1）），活化焓Δ H（双刃剑）为89 +/- 10 kJ mol（-1），活化熵DeltaS（双刃剑）为16 +/- 2 JK（-1）mol（-1）。先前对于BPTI和细胞色素c的Tyr和Phe环翻转发现的HPr的Δ V（双匕首）和Δ H（双匕首）值落在Δ V（双匕首）28至51 mL mol（-1）和Δ H（双匕首）71至155 kJ mol（-1）的范围内。相当常见的DeltaV（双匕首）和DeltaH（双匕首）值被认为分别代表在球状蛋白质的核心部分中环翻转所需的额外空间或空腔以及创建空腔所需的额外能量。几乎完全的冷变性被发现发生在200 MPa和257 K独立的环重取向过程。
Infrequent structural fluctuations of a globular protein is seldom detected and studied in detail. One tyrosine ring of HPr from Staphylococcus carnosus, an 88-residue phosphocarrier protein with no disulfide bonds, undergoes a very slow ring flip, the pressure and temperature dependence of which is studied in detail using the on-line cell high-pressure nuclear magnetic resonance technique in the pressure range from 3 MPa to 200 MPa and in the temperature range from 257 K to 313 K. The ring of Tyr6 is buried sandwiched between a P-sheet and alpha-helices (the water-accessible area is less than 0.26 mm(2)), its hydroxyl proton being involved in an internal hydrogen bond. The ring flip rates 10(1)similar to10(5) s(-1) were determined from the line shape analysis of H-delta1,H-delta2 and H-epsilon1,H-epsilon2 of Tyr6, giving an activation volume DeltaV(double dagger) of 0.044 +/- 0.008 nm(3) (27 mL mol(-1)), an activation enthalpy DeltaH(double dagger) of 89 +/- 10 kJ mol(-1), and an activation entropy DeltaS(double dagger) of 16 +/- 2 JK(-1) mol(-1). The DeltaV(double dagger) and DeltaH(double dagger) values for HPr found previously for Tyr and Phe ring flips of BPTI and cytochrome c fall within the range of DeltaV(double dagger) of 28 to 51 mL mol(-1) and DeltaH(double dagger) of 71 to 155 kJ mol(-1). The fairly common DeltaV(double dagger) and DeltaH(double dagger) values are considered to represent the extra space or cavity required for the ring flip and the extra energy required to create a cavity, respectively, in the core part of a globular protein. Nearly complete cold denaturation was found to take place at 200 MPa and 257 K independently from the ring reorientation process.