THE PRIMARY STRUCTURE OF THE ELONGATION FACTOR-G FROM ESCHERICHIA-COLI - AMINO-ACID-SEQUENCE OF THE C-TERMINAL DOMAIN
THE PRIMARY STRUCTURE OF THE ELONGATION FACTOR-G FROM ESCHERICHIA-COLI - AMINO-ACID-SEQUENCE OF THE C-TERMINAL DOMAIN
复制标题
DOI：
10.1016/0014-5793(81)80237-2
复制
发表时间：
1981-01-01
期刊：
影响因子：
3.5
通讯作者：
OVCHINNIKOV, YA
中科院分区：
文献类型：
--
作者：
ALAKHOV, YB;DOVGAS, NV;OVCHINNIKOV, YA
延伸因子G的温和蛋白水解将其分裂成有限数量的片段[1 -3]。两个片段Ta和T（来自[2]的命名法）包含整个蛋白质多肽链。片段Tz代表EF-G分子的N端部分，Mr为56 000，片段T5代表EF-G分子的C端部分，Mr为25 000。就其多肽链的一般包装而言，这些片段代表EF-G分子中的单个结构单元或结构域[4]。EF-G中酪氨酸残基修饰的研究[51]表明，用四硝基甲烷或碘修饰可使蛋白质在核糖体依赖性GTdR反应中失活。进行修饰的酪氨酸残基位于C-末端结构域（片段Ts），并通过EF-G与70 S核糖体或50 S亚颗粒结合而有效保护其免受修饰。在结合位点位于N-末端结构域（片段T的N-末端部分）的鸟苷酸存在下[6]，修饰速率显著高于游离蛋白。由于酪氨酸残基的修饰不影响EF-G与鸟苷酸形成二元复合物的能力[51]，并考虑到核糖体对修饰的屏蔽效应，因此可以得出结论，C-末端结构域包含与核糖体相互作用的位点之一。EF-G的N-和C-末端部分与GTP相互作用可能形成与核糖体相互作用的共同位点;该位点在与核糖体的复合物内的GTP水解后消失;结果，EF-G失去对核糖体的亲和力。
Mild proteolytic hydrolysis of the elongation factor G splits it into a limited number of fragments [l-3]. Two fragments, Ta and T,(nomenclature from [2]) encompass the whole protein polypeptide chain. Fragment Tz represents the N-terminal part of the EF-G molecule with Mr 56 000 and fragment T5 the C-terminal part withMr 25 000. In terms of general packing of their polypeptide chains, these fragments represent individual structural units or domains in the EF-G molecule [4].The study of modification of tyrosine residues in EF-G [51 has shown that modification with either tetranitromethane or iodine inactivates the protein in the ribosome-dependent GTPase reaction. Tyrosine residues subjected to modification are located in the C-terminal domain (fragment Ts) and are effectively protected against modification by EF-G binding with the 70 S ribosome or the 50 S subparticle. In the presence of guanyl nucleotides whose binding site is located in the N-terminal domain (in the N-terminal part of fragment T,)[6] the rate of modification is considerably higher than in the free protein. Since modification of tyrosine residues does not affect the ability of EF-G to form binary complexes with guanyl nucleotides [51 and taking into account the shielding effect exerted by the ribosome on modification it has been concluded that the C-terminal domain contains one of the sites of interaction with the ribosome. It is possible that N-and C-terminal parts of EF-G interacting with GTP form a common site of interaction with the ribosome; this site disappears after GTP hydrolysis within the complex with the ribosome; as a result, EF-G loses affinity for the ribosome.