The core region of human glutaminyl-tRNA synthetase homologies with theEscherichia cotiand yeast enzymes

Abstract

We have isolated from a Lambda-gt 11 library a human cDNA clone with one open reading frame of about 2400 bases. A stretch of about 350 amino acids in the deduced amino acid sequence is up to 40 percent identical with parts of the known amino acid sequences of E. coli and yeast glutaminyl (Gln)-tRNA synthetase. The isolated cDNA sequence corresponds to an internal section of a 5500 bases long mRNA that codes for a 170 kDa polypeptide associated with Gln-tRNA synthetase. Thus, the human enzyme is about three times larger than the E. coli and two times larger than the yeast Gln-tRNA synthetase. The three enzymes share an evolutionarily conserved core but differ in amino acid sequences linked to the N-terminal and C-terminal side of the core.

A component of the multisynthetase complex is a multifunctional aminoacyl-tRNA synthetase.

“…The longest cloned amplified (p191) sequence was 250 bp long and, as expected, partially overlapped with the XZ7 cDNA ( Figure 1). (Thommes et al, 1988) which has been tentatively assigned to human glutaminyl-tRNA synthetase (see Discussion), and to its recently published full-length sequence (Fett and Knippers, 1991 (Schimmel, 1987) at position 217, and a derivative of the KMSKS consensus sequence (Hountondji et al, 1986), VLSKR at position 438. Therefore, this protein domain belongs to class I aminoacyl-tRNA synthetases (Eriani et al, 1990a).…”

“…The observation that antibodies raised against the cDNA-encoded protein allowed immunoprecipitation of glutaminyl-tRNA synthetase activity (Thommes et al, 1988), which is also one of the synthetase components of the complex containing glutamyl-tRNA synthetase, does not prove the identity of the human protein. Indeed, any antibody able to recognize one of the entities of the multisynthetase complex co-immunoprecipitates all of the other components (Mirande et al, 1982c).…”

Reaction of anti-OJ autoantibodies with components of the multi-enzyme complex of aminoacyl-tRNA synthetases in addition to isoleucyl-tRNA synthetase.

“…The identity ofband a in the human synthetase complex is not settled, but glutaminyl-tRNA synthetase (20,21 ) or a multifunctional synthetase showing both glutamyl-tRNA synthetase and prolyl-tRNA synthetase activity (22) have been proposed. Protein band b appears to be IleRS, as determined by molecular mass ( 140-150 kD for IleRS) and position in the complex ( 15,20). The 140-kD protein band was of slightly higher molecular weight than band c, consistent with the other evidence that it was not part of the synthetase complex.…”

“…Studies of the cDNA sequence coding for the largest component (reported as 170 kD) noted homology with bacterial glutaminyl-tRNA synthetase and assigned the identity of glutaminyl-tRNA synthetase to the protein on that basis (20,21 ). However, previous studies of the complex in other mammals identified the highest molecular weight component as glutamyl-tRNA synthetase ( 15 ).…”

Alanine Transfer RNA Synthetase: Structure–Function Relationships and Molecular Recognition of Transfer RNA

“…On the other hand, seven of the enzymes have been shown to share a short common sequence element (the signature sequence), which is an essential part of the nucleotide fold that is in the amino terminal half of each polypeptide (3). These include glutamic (9), glutamine (10)(11)(12), isoleucine (13,14), leucine (15), and valine (16)(17)(18) tRNA-synthetases (all monomers), and the methionine (19,20) and tyrosine (21)(22)(23)(alpha2 dimers) enzymes. The tryptophan enzyme (alpha2 dimer) may also have a signature sequence element (24)(25)(26).…”