Francklyn C, Schimmel P
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Proc Natl Acad Sci U S A. 1990 Nov;87(21):8655-9. doi: 10.1073/pnas.87.21.8655.
The major determinant for the identity of alanine tRNAs is a single base pair in the acceptor helix that is proximal to the site of amino acid attachment. A 7-base-pair microhelix that recreates the acceptor helix can be charged with alanine. No other examples of charging of small helices with specific amino acids have been reported, to our knowledge. We show here that a 13-base-pair and an 8-base-pair hairpin helix that reconstruct a domain and subdomain, respectively, of histidine tRNAs can be charged with histidine. We also show that transplantation of a base pair that is unique to histidine tRNAs is sufficient to consider histidine acceptance on a domain and subdomain of alanine tRNA. Both alanine and histidine aminoacyl-tRNA synthetases retain specificity for their cognate synthetic substrates. Alanine- and histidine-specific microhelices may resemble a system that arose early in the evolution of charging and coding.
丙氨酸tRNA身份的主要决定因素是氨基酸连接位点近端接受臂螺旋中的一个碱基对。一个能重建接受臂螺旋的7碱基对微螺旋可以被丙氨酸酰化。据我们所知，尚未有其他关于用特定氨基酸对小螺旋进行酰化的例子报道。我们在此表明，分别重建组氨酸tRNA一个结构域和一个亚结构域的13碱基对和8碱基对发夹螺旋可以被组氨酸酰化。我们还表明，移植组氨酸tRNA特有的一个碱基对足以使丙氨酸tRNA的一个结构域和一个亚结构域接受组氨酸。丙氨酸和组氨酸氨酰-tRNA合成酶对其同源合成底物均保持特异性。丙氨酸特异性和组氨酸特异性微螺旋可能类似于在酰化和编码进化早期出现的一个系统。
