3D-Structure Prediction of the Modular Protein Sialoadhesin Using a Multi-step Modelling Strategy

Sialoadhesin (Siglec1) is a type I membrane glycoprotein of about 1600 residues length organized in 17 Ig-like domains whose reciprocal fold has not been clarified. The protein is present in different species and is implicated in diverse pathogenic processes including rhinovirus infection, Porcine Reproductive and Respiratory Syndrome (PRRS) virus infection and in HIV infections. Mammalian sialoadhesins share a high degree of similarity, and show homologies with different members of immunoglobulin superfamily. Here we propose a structural model for the first eight domains (SnD01 to Snd08) of sialoadhesin. The model is obtained by a multi-step procedure that combines homology and fold recognition approaches, and is applied to modelling of individual two-domain units. After energy profile based validation of each unit, an putative ensemble model is then proposed. The model provides a framework for localization and interpretation of polymorphisms identified in pig sialoadhesin.