Analysis of GTP addition in the reverse (3'-5') direction by human tRNA guanylyltransferase.

Human tRNA guanylyltransferase (HsThg1) catalyzes the 3'-5' addition of guanosine triphosphate (GTP) to the 5'-end (-1 position) of tRNA, producing mature tRNA In human cells, cytoplasmic and mitochondrial tRNA have adenine (A) or cytidine (C), respectively, opposite to G Little attention has been paid to the structural requirements of incoming GTP in 3'-5' nucleotidyl addition by HsThg1. In this study, we evaluated the incorporation efficiencies of various GTP analogs by HsThg1 and compared the reaction mechanism with that of Thg1 (CaThg1). HsThg1 incorporated GTP opposite A or C in the template most efficiently.

Molecular mechanism of substrate recognition and specificity of tRNA guanylyltransferase during nucleotide addition in the 3'-5' direction.

The tRNA guanylyltransferase (Thg1) transfers a guanosine triphosphate (GTP) in the 3'-5' direction onto the 5'-terminal of tRNA, opposite adenosine at position 73 (A). The guanosine at the -1 position (G) serves as an identity element for histidyl-tRNA synthetase. To investigate the mechanism of recognition for the insertion of GTP opposite A, first we constructed a two-stranded tRNA molecule composed of a primer and a template strand through division at the D-loop.

Biochemical analysis of human tRNA guanylyltransferase in mitochondrial tRNA maturation.

Mitochondria contain their own protein synthesis machinery, which includes mitochondrial tRNA maturation. It has been suggested that mammalian mitochondrial tRNA (mtRNA) is matured by post-transcriptional addition of guanosine at the -1 position (G), which serves as an identity element for mitochondrial histidyl-tRNA synthetase. However, the exact maturation process of mammalian mtRNA remains unclear.