Original scientific paper

https://doi.org/10.5562/cca1818

Substrate Recognition by Novel Family of Amino Acid:[Carrier Protein] Ligases

Marko Močibob ; University of Zagreb, Faculty of Science, Department of Chemistry, Horvatovac 102a, 10 000 Zagreb, Croatia
Nives Ivić ; Rudjer Boskovic Institute, Department of Physical Chemistry, Bijenicka 54, 10 000 Zagreb, Croatia
Deni Šubašić ; University of Zagreb, Faculty of Science, Department of Chemistry, Horvatovac 102a, 10 000 Zagreb, Croatia
Marija Luić ; Rudjer Boskovic Institute, Department of Physical Chemistry, Bijenicka 54, 10 000 Zagreb, Croatia
Ivana Weygand-Đurašević ; University of Zagreb, Faculty of Science, Department of Chemistry, Horvatovac 102a, 10 000 Zagreb, Croatia

Abstract

Amino acid:[carrier protein] ligases (aa:CP ligases) are newly discovered homologs of aminoacyl-
tRNA synthetases (aaRS) which aminoacylate carrier proteins instead of tRNA. Activated amino
acids are attached to prosthetic group of carrier proteins by thioester bond. Weak thioacylation activity
was observed for many conventional aaRS. Therefore, different thiols were investigated as substrate analogs
for aa:CP ligases. Here we show that coenzyme A, dithiothreitol and cysteine are efficiently aminoacylated
by aa:CP ligases. The crystal structure of aa:CP ligase from Bradyrhizobium japonicum in complex
with coenzyme A was solved, and revealed that CoA, besides acting as the substrate analog of the
carrier protein, also competes with ATP for binding to the active site. aa:CP ligases do not aminoacylate
tRNA, although they remarkably resemble catalytic core of atypical seryl-tRNA synthetases (aSerRS)
from methanogenic archaea. Since aa:CP ligases lack tRNA-binding domain, fusion proteins of aa:CP ligases
and aSerRS tRNA-binding domain were prepared in attempt to restore tRNA aminoacylation activity.
Although fusion proteins were able to bind tRNA through appended domain, tRNA could not substitute
carrier proteins in aminoacylation reaction. (doi: 10.5562/cca1818)

Keywords

aminoacyl-tRNA synthetase; amino acid:[carrier protein] ligase; carrier protein; coenzyme A; seryl-tRNA synthetase; thioester; tRNA

Hrčak ID:

71977

URI

https://hrcak.srce.hr/71977

Publication date:

3.10.2011.

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