Identification and characterization of a proteolysis-resistant fragment containing the PCI domain in the Arabidopsis thaliana INT6/eIF3e translation factor.
The PCI domain comprises approx 200 amino acids and is found in subunits of the eukaryotic translation initiation factor 3 (eIF3), the 26S proteasome and the COP9/signalosome complexes. The PCI domain is involved in protein-protein interaction, and mouse INT6 truncated proteins lacking the PCI domain show cell malignanttransforming activity. In this work, the Arabidopsis thaliana INT6/eIF3e (AtINT6) protein was dissected using limited proteolysis, and a protease-resistant fragment containing the PCI domain was identified. Based on mass spectrometry analyses of the protease-resistant fragments and on secondary structure prediction, AtINT6-truncated proteins were cloned and expressed in Escherichia coli. Stability studies using thermal unfolding followed by circular dichroism revealed a midpoint transition temperature of 44 degrees C for the full-length AtINT6 protein, whereas the truncated proteins comprising residues 125-415 (AtINT6TR2) and 172-415 (AtINT6TR3) showed transition temperatures of 49 and 58 degrees C, respectively. AtINT6TR3 contains the PCI domain with additional amino acids at the N and C termini. It shows high solubility, and together with the high thermal stability, should facilitate further characterization of the PCI domain structure, which is important to understand its function in protein- protein interaction.
Murai
Marcelo J
MJ
Center for Structural Molecular Biology, Brazilian Synchrotron Light Laboratory-LNLS, Campinas-SP, Brazil.
Carneiro
Flávia R G
FR
Gozzo
Fabio C
FC
Ierardi
Daniela F
DF
Pertinhez
Thelma A
TA
Zanchin
Nilson I T
NI