Biomedical subjects

Kazuma Takada

Publications and source records attributed to Kazuma Takada.

5 recordsLinked to original sources

PubMed2005

Competition between trans-translation and termination or elongation of translation.

The effects of tRNA, RF1 and RRF on trans-translation by tmRNA were examined using a stalled complex of ribosome prepared using a synthetic mRNA and pure Escherichia coli translation factors. No endoribonucleolytic cleavage of mRNA around the A site was found in the stalled ribosome and was required for the tmRNA action. When the A site was occupied by a stop codon, alanyl-tmRNA competed with RF1 with the efficiency of peptidyl-transfer to alanyl-tmRNA for trans-translation inversely correlated to the efficiency of translation termination. The competition was not affected by RF3. A sense codon also serves as a target for alanyl-tmRNA with competition of aminoacyl-tRNA. The extent of inhibition was decreased with the length of the 3'-extension of mRNA. RRF, only at a high concentration, slightly affected peptidyl-transfer for trans-translation, although it did not affect the canonical elongation. These results indicate that alanyl-tmRNA does not absolutely require the truncation of mRNA around the A site but prefers an mRNA of a short 3'-extension from the A site and that it can operate on either a sense or termination codon at the A site, at which alanyl-tmRNA competes with aminoacyl-tRNA, RF and RRF.

Alanine↗

PubMed2005

Functional analysis of factors involved in trans-translation.

trans-translation is a rescue system for stalled ribosomes to terminate the translation for recycling of ribosome and lead the incomplete protein on the stalled ribosome to degradation. In trans-translation, several proteins and RNAs are involved. tmRNA and SmpB are only factors known to be essential for trans-translation. EF-Tu and EF-G functions in translation and also are seemed to function in trans-translation. Ribosomal protein S1 is known to bind tmRNA. In this study, we cloned the gene of tmRNA from Thermus thermophilus and analyzed the functions of factors involved in trans-translation in vitro.

Base Sequence↗

PubMed2003

In vitro analysis of the initial steps of trans-translation.

tmRNA has a dual function both as tRNA and mRNA and facilitates trans-translation. We observed the tagging derived from tmRNA from Bacillus subtilis in vivo and in vitro. Our studies give progressive suggestions on the mechanism of trans-translation.

Bacillus subtilis↗

PubMed2002

Trans-translation mediated by Bacillus subtilis tmRNA.

Trans-translation, in which a ribosome switches between translation of an mRNA and a tmRNA, produces a chimera polypeptide of an N-terminal truncated polypeptide and a C-terminal tag-peptide encoded by tmRNA. One of the tmRNA binding proteins, a ribosomal protein S1, has not been found in a group of Gram-positive bacteria. In this study, the trans-translation reaction with tmRNA from Bacillus subtilis belonging to this group was examined. When a truncated gene lacking a termination codon was expressed in B. subtilis, a 15-amino acid tag-peptide derived from tmRNA was identified in the C-termini of the trans-translation products. An identical tag-peptide was also found at the C-termini of the products from a truncated gene, when it was coexpressed with B. subtilis tmRNA in Escherichia coli. B. subtilis tmRNA was functional, although much less efficiently, in the in vitro poly(U)-dependent tag-peptide synthesis system of E. coli. A comparison of two bacterial tmRNAs suggests that the rule for determining the tag-initiation point on tmRNA may be the same in Gram-positive and Gram-negative bacteria.

Amino Acid Sequence↗

PubMed2002

The structure and function of tmRNA.

tmRNA has a dual function both as tRNA and mRNA and facilitates trans-translation. We made various mutation in tRNA domain of tmRNA. Our mutation studies give progressive suggestions on the structure of tmRNA.

Mutation↗