First Identification, Recombinant Production, and Structural Characterization of a Putative Structural Protein from...

Area of Science:

• Virology
• Structural Biology
• Bioinformatics

Background:

• Haseki tick virus (HSTV) is a recently identified virus transmitted by ticks.
• The protein composition of HSTV is largely unknown, hindering further research.
• Understanding viral protein structure is crucial for diagnostics and therapeutics.

Purpose of the Study:

• To characterize the structural protein repertoire of HSTV.
• To determine the three-dimensional structure of the HSTV structural protein 1 (SP1).
• To establish a pipeline for analyzing divergent viral proteins.

Main Methods:

• Integrative approach combining membrane topology prediction, AI-based structural prediction, and experimental validation.
• Recombinant expression of HSTV SP1.
• Small-angle X-ray scattering (SAXS) for determining protein architecture in solution.
• Comparative structural analysis with known viral proteins.

Main Results:

• The study determined the overall architecture of HSTV SP1 using SAXS.
• AI-predicted models of HSTV SP1 showed only slight resemblance to pestiviral proteins Erns and Npro.
• Experimental SAXS data strongly agreed with AI-predicted models, confirming HSTV SP1's distinct spatial structure.
• HSTV SP1 adopts a novel fold not previously seen in the Flaviviridae family.

Conclusions:

• HSTV SP1 possesses a unique structural fold, distinct from other characterized Flaviviridae members.
• Modern AI-based prediction accurately represents the spatial architecture of HSTV SP1.
• This study provides the first structural insights into HSTV SP1, a virus with zoonotic potential.
• The developed methodological pipeline can characterize highly divergent viral proteins.