InterPro domain: IPR010978

This superfamily represents an alpha-helical tRNA-binding arm found in class I and II aminoacyl-tRNA synthetase enzymes, as well as in the methicillin resistance protein FemA.

The tRNA-binding arm domain is conserved between class I and class II aminoacyl-tRNA synthetase enzymes ( 6.1.1. ), consisting of two alpha helices in an antiparallel hairpin with a left-handed twist. The appended tRNA-binding domains recognise a small number of nucleotides that are conserved specifically in each cognate tRNA species for the discrimination between the cognate and noncognate tRNAs [ 1 ]. These nucleotides are called identity elements, and constitute the identity set. The tRNA-binding arm occurs as the C-terminal domain in some class I enzymes, such as valyl-tRNA synthetase, and as the N-terminal domain in some class II enzymes, such as phenylalanyl-tRNA synthetase.

The methicillin resistance protein, FemA (factors essential for methicillin resistance), contains a probable tRNA-binding arm that is similar in structure to those found in tRNA synthetases. In FemA, the tRNA-binding arm is inserted into the C-terminal NAT-like domain, and is thought to bind tRNA-glycine. FemA, along with FemB and FemX, plays a vital role in peptidoglycan biosynthesis specific to Staphylococci [ 2 ].

1. Mechanism of molecular interactions for tRNA(Val) recognition by valyl-tRNA synthetase. RNA 9, 100-11
2. X-ray crystal structure of Staphylococcus aureus FemA. Structure 10, 1107-15