AlaRS-DELTAC, comprising the aminoacylation, tRNA-recognition, and editing domains, and AlaRS-C, comprising the dimerization domain. The aminoacylation/tRNA-recognition domains contain an insertion incompatible with the class-specific tRNA-binding mode. The editing domain is fixed tightly via hydrophobic interactions to the aminoacylation/tRNA-recognition domains, on the side opposite from that in threonyl-tRNA synthetase. A groove formed between the aminoacylation/tRNA-recognition domains and the editing domain appears to be an alternative tRNA-binding site. The amino acid residues required for the G3:U70 base pair recognition are mapped in this groove. The dimerization domain consists of helical and globular subdomains. The helical subdomain mediates dimerization by forming a helixloophelix zipper. The globular subdomain, which is important for the aminoacylation and editing activities, has a positively-charged face suitable for tRNA binding |
Archaeoglobus fulgidus |