Characterization of cDNAs and genomic DNAs for human threonyl- and cysteinyl-tRNA synthetases
Techniques of molecular biology were used to clone, sequence and map two human aminoacyl-tRNA synthetase (aaRS) cDNAs: threonyl-tRNA synthetase (ThrRS) a class II enzyme and cysteinyl-tRNA synthetase (CysRS) a class I enzyme. The predicted protein sequence of human ThrRS is highly homologous to that of lower eukaryotic and prokaryotic ThRSs, particularly in the regions containing the three structural motifs common to all class II synthetases. Signature regions 1 and 2, which characterize the class IIa subgroup (SerRS, ThrRS and HisRS) are highly conserved from bacteria to human. Structural predictions for human ThrRS based on the known structure of the closely related SerRS from E.coli implicate strongly conserved residues in the signature sequences to be important in substrate binding. The amino terminal 100 residues of the deduced amino acid sequence of ThrRS shares structural similarity to SerRS consistent with forming an antiparallel helix implicated in tRNA binding. The 5' untranslated sequence of the human ThrRS gene shares short stretches of common sequence with the gene for hamster HisRS including a binding site for the promoter specific transcription factor sp-1. The deduced amino acid sequence of human CysRS has a high degree of sequence identify to E. coli CysRS. Human CysRS possesses the classic characteristics of a class I synthetase and is most closely related to the MetRS subgroup. The amino terminal half of human CysRS can be modeled as a nucleotide binding fold and shares significant sequence and structural similarity to the other enzymes in this subgroup. The CysRS structural gene (CARS) was mapped to human chromosome 11p15.5 by fluorescent in situ hybridization. CARS is the first aaRS gene to be mapped to chromosome 11. The steady state of both CysRS and ThrRs mRNA were quantitated in several human tissues. Message levels for these enzymes appear to be subjected to differential regulation in different cell types.
- Research Organization:
- California Univ., Irvine, CA (United States)
- OSTI ID:
- 7071010
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
550400* -- Genetics
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
CARBOXYLIC ACIDS
CLONING
CYSTEINE
DNA SEQUENCING
ENZYMES
GENETIC MAPPING
HUMAN POPULATIONS
HYDROXY ACIDS
LIGASES
MAPPING
MOLECULAR BIOLOGY
NUCLEIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
POPULATIONS
PROTEINS
RNA
STRUCTURAL CHEMICAL ANALYSIS
THIOLS
THREONINE
TRANSFER RNA