Conserved dimerization architecture in C-type lectins from virus-vector mosquitoes

Area of Science:

• Structural biology
• Vector-borne disease research
• Immunology

Background:

• C-type lectins (CTLs) are vital for immunity and recognizing microbial carbohydrates.
• The C-type lectin domain-single (CTLD-S) family in Aedes aegypti mosquitoes has 34 members involved in flavivirus dissemination and microbial balance.
• The structural organization of these CTLs has not been previously characterized.

Purpose of the Study:

• To structurally characterize C-type lectins (CTLs) in the Aedes aegypti mosquito.
• To investigate the organization and potential dimerization of the CTLD-S protein family.
• To understand the implications of CTL organization for glycan binding and vector-pathogen interactions.

Main Methods:

• X-ray crystallography was used to determine the structures of four representative CTLD-S proteins.
• Small-angle X-ray scattering (SAXS) and molecular dynamics simulations were employed to study protein behavior in solution.
• Machine learning, including AlphaFold, was utilized for structure prediction and analysis of potential heterodimers.

Main Results:

• The crystal structures revealed a consistent homodimer arrangement for four mosGCTL proteins, with carbohydrate-binding sites on the same face.
• Dimerization was confirmed in solution, and computational predictions suggest it's a common feature across the CTLD-S family.
• One structure demonstrated Ca2+-dependent binding of paucimannose glycans by a dimer, and predictions suggest numerous possible heterodimers with varied glycan-binding specificities.

Conclusions:

• A conserved dimeric arrangement exists among Aedes aegypti mosquito CTLs.
• This dimerization likely plays a fundamental role in how these lectins recognize ligands, particularly carbohydrates.
• The findings provide insights into molecular mechanisms relevant to vector immunity and the spread of diseases like flavivirus.