DIPHTHAMIDE BIOSYNTHESIS

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 翻译后修饰可以使基因产物的功能特性多样化，是生物学中广泛使用的策略。 邻苯二甲酰胺[2，3-羧酰胺基-3- [（三甲基铵基）丙基组氨酸]是在真核生物和古细菌的翻译延伸因子2中发现的保守的经化学修饰的组氨酸残基。 联苯二胺的功能仍是研究的课题。 例如，缺乏修饰的酵母突变体已被鉴定为具有不受抑制的生长和活力（Chen等人，Mol. Cell Biol.1985）。 然而，在蛋白质合成过程中，二苯二甲酰胺残基似乎具有防止-1移码的功能（Gomez-Lorenzo et al. EMBO J. 2000），并且也是白喉毒素以及铜绿假单胞菌外毒素A的ADP-核糖基化靶标。 邻苯二胺的生物合成是一个复杂的过程，涉及真核生物中的6种蛋白质dph 1 -5和一种尚未鉴定的酶，该酶执行最后的酰胺化步骤。 第一步涉及从S-腺苷甲硫氨酸（SAM）转移3-氨基-3-羧丙基，并涉及酶dph 1 -4。 Dph-5催化氨基的三甲基化，形成最后酰胺化步骤的底物diphthine。 有趣的是，在古细菌中只发现了2种基因产物参与了联苯二酰胺的合成，dph-2和dph-5。 对古细菌dph-2进行了结构研究，以便深入了解联苯二酰胺的生物合成途径。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Post-translational modifications can diversify the functional properties of gene products and is a widely-utilized strategy in biology. Diphthamide [2,3-carboxyamido-3- (trimethylammonio)propyl histidine] is a uniquely-modified histidine residue found conserved in translation elongation factor 2 from both eukaryotes and archaebacteria. The function of diphthamide is still the subject of research. For example, yeast mutants lacking the modification have been identified with uninhibited growth and viability (Chen et al. Mol. Cell Biol. 1985). However, the diphthamide residue appears to have function in preventing -1 frameshifting during protein synthesis (Gomez-Lorenzo et al. EMBO J. 2000) and is also the ADP-ribosylation target of diphtheria toxin as well as Pseudomonas aeruginosa exotoxin A. The biosynthesis of diphthamide is a complex process that involves 6 proteins in eukaryotes, dph1-5 and an as-yet unidentified enzyme that performs a final amidation step. The first step involves the transfer of the 3-amino-3-carboxypropyl group from S-adenosylmethionine (SAM) and involves the enzymes dph1-4. Dph-5 catalyzes trimethylation of the amino group to form diphthine, the substrate for the final amidation step. Interestingly, only 2 gene products have been identified in archaebacteria to be involved in diphthamide synthesis, dph-2 and dph-5. Structural studies have been undertaken on archaebacterial dph-2 in order to provide insight into the diphthamide biosynthetic pathway.