Journal of Bacteriology & Parasitology

A biochemical study of auto-inhibition of importin α in an apicomplexan parasite, Toxoplasma gondii

10^th International Confernce on Parasitology, Microbiology and Infection Control

November 08-09, 2022 | Webinar

Manasi Bhambid

Dept. of Biosciences & Bioengineering, Indian Institute of Technology, INDIA

Scientific Tracks Abstracts: J Bacteriol Parasitol

Abstract:

Statement of problem: Nuclear proteins contain classical nuclear localisation signals that bind to the NLS-binding sites of the nuclear transporter, importin α. A domain in IMPα, the importin β-binding (IBB) domain, has an NLSlike cluster and forms an intramolecular interaction with the NLS-binding site; termed auto-inhibition. Studies on the seven Homo sapiens IMPα proteins show varying levels of auto inhibition, despite no differences in the NLS-like cluster. On the contrary, the single isoform of Plasmodium falciparum IMPα lacks auto-inhibition. This phenotype was traced back to the serine present in the NLS-like cluster. Another parasite, Toxoplasma gondii, also harbours a single IMPα isoform, and the residues in the NLS-like cluster are similar to those of H. sapiens. We asked whether TgIMPα shows auto-inhibition and specifically tested the strength of auto-inhibition of the protein Methodology: Auto-inhibition strength was determined by in vitro NLS-binding studies with the full-length and ΔIBBTgIMPα. In silico research involved a structure prediction model, docking IBB at the NLS-binding site and phylogeny study. The observations made in silico approaches were tested in vitro. Findings: Our work shows that the single isoform of TgIMPα exhibits auto-inhibition, which appears to be consistently weaker than that seen for mammalian and plant IMPα proteins. Sequence analysis and structural modelling of TgIMPα suggest that the protein has two novel features: the IBB domain is predicted to be a helical structure, and between the IBB and the NLS-binding sites, there is a longer hinge motif. The contribution of these features is being studied using biochemical techniques. Conclusion and Significance: A consistently weak autoinhibition is observed to confer an advantage in proliferation and protein transport in human cell lines. Our work shows that a lack of/weak auto-inhibition is a common feature of two Apicomplexan IMPα proteins. The biological implications of this phenotype are being studied.

Biography :

Manasi has done extensive bioinformatics and in silico analysis to understand the basis of the auto-inhibition strength in T. gondii IMPα. This apicomplexan protein’s lack of structural information has led her to look for explanations through structure prediction models and phylogenetic tree construction. Her work has given some novel insights into the protein structure, and she is geared up to test her hypothesis experimentally. The fine-tuning of the auto-inhibition strength of this essential nuclear transporter protein will be further studied in the context of the biology of Toxoplasma gondii.